Usage:

1. Upload a .schematic file. For big schematics it will take longer obviously

2. Choose your command type.

The "/setblock" command type will make a .mcfunction file with all the commands needed to recreate your schematic except rotations (Example 1).

The "/execute as" command type does the same but will give you the option the give a selector. (Example 2)

The selector can be @a, @e, @p, @r or @s (It can even be @e[type=zombie,tag=123,nbt={fakescore:123b,Health:10..f}] ). It is better if you use the selector *before* you run the function and skip this option but you can use this as well. For example: "execute as @a run setblock ~ ~-1 ~ sandstone" would be the outcome of your .mcfunction file if your .schematic would have one sandstone piece below you and the region is 1 by 1 block. If the region is a higher volume than the blocks in it, and you want the regions' air blocks to convert as well? the following feature comes in handy:

3. With the "Build with air" feature the generator will make the .mcfunction file also contain the air blocks in your schematic file (Example 3).