It's a little work, but really not that much, it's cutting off two bottoms, cutting a strip to put inside as a "wall", opening up 1 bottom, slide it in eachother and you're good.
You slide one inside the other by just crimping the edges of one a little bit, then you can slide it in. also possible to heat one and cool another. There's no need for any kind of weld or glue or anything. It can help, but isn't needed. I just have some extra jets around the edges