I made a former from some round bar with lumps added to the side. Then got some scaffold tube and machined the galvanising off it. Heat it up red hot and press former into it. Removed former put pipe in lathe and machined the flange end square, cut to length and TAA DAA a flange.
looks like a good start on your exhaust project.
Two more and you're ready to begin.
come to think of it, you better do up several sets of three,
might not work out the first time round.
but good luck never the less, and can't wait to see what you come up with.