So a game called "Dominions 4" has a built in map-making process, however it is wildly unpredictable when it comes to land mass shapes.

After many, many tries I finally landed on a map that suited my DnD purposes.

The map is such: https://i.imgur.com/yxcsQw1.png

Here is the same map with the desired changes listed as instructions: https://i.imgur.com/qnnsi7y.jpg