After establishing the basic premise of the Exalted campaign in the last post, let's get started on the actual sandbox! For this, we need to generate a hex map of the area that interests us. Which, for the purpose of this campaign, means An-Teng and its surrounding areas. There are many ways of doing this, but I will walk you through my approach.
First, you will need Inkscape, a free Open Source vector-based graphics program. Vector-based graphics software has the advantage that its images can be very easily scaled, which we will need. For further processing you will also need some bitmap-based graphics software. I generally use GIMP, since that's what I am used to, but these days I am also eyeing Krita, which has a better collection of virtual brushes. Both are also free Open Source products.
Next we need to decide on the map scale - the size of each individual hex. After some deliberation I've decided to go with 25 miles hexes (side to side) - a fairly large scale (I used 10 miles hexes in the Cold Frontier campaign), but as we will see later, that still gives us plenty of hexes to cover - and it fits the "Fives" theme of Exalted, too. And while I do want to encourage a sandbox approach in this campaign, the goal of an Exalted campaign cannot be to explore every last space on the map, so we should pick a map scale that makes each location at least moderately important.
Now we need both pre-existing setting maps and a hex grid that we can put on top of them. First, I started with the Exalted 3E map of Creation that is floating around the Internet - this is the best version I could find. Then I opened up the Layer menu in Inkscape ("Layer->Layers...") and created a new layer, giving the layer the name "Creation Map". I then loaded the map of Creation into this layer via "File->Import" and locked the layer (by clicking on the "lock" symbol) - this makes sure that the image doesn't get moved around or altered when I work on other stuff.
Then I copied the map of An-Teng from Compass of Terrestrial Directions IV: The South and imported it into a new layer (entitled "An-Teng Map"). Then, using the "Select and transform objects tool" (the black arrow thingie at the top of the tool menu) I moved this map around and scaled it until its coastline roughly matched up with the larger map of Creation (tip: press on "Ctrl" while scaling this image so that the ratio of the sides will remain the same). This way, we can use the scale and surrounding areas of the larger Creation map while still using the details from the smaller An-Teng map.
Next, we need a suitable hex grid which we can lay over the map. There are a number of different free hex grid generators available online - sadly, my favorite is currently offline, but I will just recycle the hex grid I used for my Cold Frontier campaign. It's in the SVG format, which is what Inkscape uses natively, and has 11x8 hexes on a single "page", which I found useful in my old campaign.
Now we need to scale it to a suitable size. The Creation map has a scale in the middle of the ocean, which allows us to determine what a distance of 500 miles represents - which is equal to 20 hexes in the hexgrid.
Thus, we import the hex grid into our Inkscape file - again using a new layer (entitled "Hex Scale"). Since the map scale is shown horizontally but the hex grid is aligned vertically, we first need to rotate the grid by 90 degrees (via "Object->Rotate 90° CW"). Then, since a single grid only has a length of 11 hexes, we copy and paste the grid and place the second one next to it, so that the two grids fit into each other precisely. Then we select both of the grid and scale and move them so that the 500 mile map scale is covered by exactly 20 hexes. The end result should look something like this:
Now the hex grid has the correct scale, and all we need to do is rotate it back (via "Object->Rotate 90° CCW") - then we can copy and paste it over all the places we are interested in (do that on a new layer, though - and lock the old layer to make sure you don't lose the scale). The end result could look something like this:
If you prefer drawing maps on paper, you could just print this out and draw the map anew on empty hex paper. However, personally I prefer to draw maps digitally - a halfway decent graphics program (and GIMP is entirely sufficient for this purpose) and a graphics tablet make this process a lot more fun in my opinion. While I use my Wacom Cintiq these days, a vastly cheaper Wacom Baboo tablet (which you can get for less than a hundred bucks) works as well.
For this process, select the single hex grid of the area you want to start with. Then go on "File->Export Bitmap...", and make sure that the "Selection" option is chosen. Pick a bitmap size you are comfortable with (I generally choose a height of 1000-1200 pixels for this purpose) and export it (it might be helpful later on if you also note the resolution - that is, the dpi value - as well).
Then open up the image with GIMP. This gives you a base background image you can paint over - but before we start painting, there is one important further step. Go on "File->Open as Layer" - and import the empty hex grid in SVG format. If you choose the same height for the hex grid as you have for your background image, then the new grid should appear exactly on top of the background grid.
Lock this new layer in the Layer menu of GIMP. From now on, no matter what you paint over the background image, the grid itself will remain.
How to draw maps is beyond the scope of this post - there are plenty of tutorials online you can look up - but the end result should be a hex map with the basic terrain features which you then can use for your further work.
And as a final note, you can even re-import this into your original Inkscape map and align it with its grid - this way, you can slowly piece a large map together by adding the regional maps you created.
But that's enough for map-making for the time being - now we need to fill it up with locations!