Here are some smoosher setups I have.
For BB pinches I use two pieces of 2x4 about 2’ long, connected with a gate hinge at one end. Stick the tube in there and smoosh it in the hydraulic press.
I did make some fancy aluminum dies for top tube smooshes at the ST. I just smoosh them in the vice.
I can’t find any photos of my full tube smoosher but basically that is just a piece of real thick 2x3" steel square tube with some uprights welded on to help keep everything lined up nice then I sandwich 2x3, 1/8 aluminum plate, tube, aluminum plate, 2x3 and put that in the hydraulic press.
Don’t overthink it! Unless you want to.