How do I let things craft, when they collide with each other?

You have to put your ground_item in a family, so you have it as sprite and as family otherwise you can't compare it.

Then you could do it like that:

The compare condition looks like that:

The 'sprite.AnimationFrame=firstItem&Sprites.AnimationFrame=secondItem' are an And-Expression and if is true it's 1.

firstItem and secondItem are the frames you want to compare.