Here's my 3-part series on creating autotiles! Each video has chapter links in the youtube description so you can skip around. Part 1 covers how autotiles work (see diagram below), the differences between A1-A5, borderlines, counters, etc. Part 2 shows how to create a standard seamless tile -- skip this if you already know how. Part 3 shows how to make an autotile! Follow my order and it's dead simple, and you really don't have to worry about whether things will line up! I show some advanced Photoshop tricks to speed up the process, but you can also use simple tools like the eraser.