The first step was combining the two maps and drawing them by hand and I was pretty eager to take a crack at that. It's pretty simple compared to some of the other maps I've drawn since taking that cartography course awhile back. That's mostly because this map was only ever meant to become a draft for a carving. All the fancy detail that makes it spiffy would be done on the leather. To fill in some of the empty space between the regions we added some of the critters those areas were known for (most of which were traced right off the official 5e art).
As is typical for these longer term projects I took daily pictures to send progress updates once the carving started. The transfer wasn't as clean as I'd hoped (argh) but by this point I'd drawn, sketched, or drafted the map more than a few times. I was able to fill in the details free-hand. Then I added some stain to the oceans. That particular stain doesn't always apply smoothly with a brush (as evident here) or work happily with an overcoat but I used an interim coat to smooth it out and give it some shine. This map has shiny waters, which is pretty cool.
This was the second map that I stitched together and since the glue was already starting to give before the stitching was complete I'm pretty glad I gave it that extra step. It's a bit nerve-wracking to take a power drill to the leather knowing that one twitch or mistake will negate a week of work but the result is worth it.