Y'know, I'm honestly not sure why you're having such trouble with GIMP. I'll grant you it isn't as powerful as Photoshop, but it shouldn't be fucking up on you with something as simple as cutting out a part of something to make into a layer.
I mean, I know there are people who can make better collages than me, but
I like to think mine are decent, and I make them with GIMP. I'd say they're up to the standards of that Elvira example you posted.