Is it possible?

[DazzleMea]

To join the side of a piece to a top or bottom of another? Would it be strong?

I ask because I'm making a market bag. I've only ever knit flat stuff before, and even then I barely know what I'm doing. I taught myself not too long ago (source: some website), and their videos weren't terribly helpful....and some weren't even there. Not like this site which has the best videos and explanations - ever!