Most habaki are silver soldered or brazed (not the soft solder like stay-bright).I just assemble two sections of one side and one end,both a little oversized.It makes a "L" shape.File and fit both "L" pieces on the blade until they are snug and perfectly filed to make even joints where the two pieces meet.Don't worry about the extra sticking out from the sides,you will trim that off after soldering.Clamp them in place and scribe a line on the extra sticking out on both sides.Unclamp,and reposition them together,without the blade.Use soldering tweezers as a clamp and silver solder the assembly together.After pickling,carefully file the inside of the joints and you should be able to slip the habaki right on for a snug fit.
If you do a google search on "habaki" you will find several tutorials on assembling and fitting habaki.
Hope this helps.
Stacy