These RPG Maker tile-sets are based on 8x8 sub-tiles, but they are meant to be used on a 16x16 grid only.
That’s why you can’t really find a good way to do this with Godot’s auto-tiling. RPG Maker has an algorithm that creates 16x16 tiles out of multiple 8x8 sub-tiles.
With this particular tile-set, with large sections of plain color, you might still get away with the other suggested method, but if the middle 16x16 base tile has a texture that isn’t tileable on an 8x8 grid, then I#m pretty sure it isn’t possible to do this with Godot’s current auto tiling without some extra code.