There are several ways to make a new handle depending on the tools and skill level available.
1) Is to clamp a block of handle material down (never try to hold it in your hand) drill the necessary size hole in it and epoxy the tang in. This is better if there is a hole in the tang so it can also be pinned. The epoxy must fill any voids in the handle and around the tang or they will become week spots.
2) This will require two pieces of handle material. make both completely flat so that they will fit tightly together. then ether use a router, or a drill and a wood chisel to make a void for the tang to fit in. glue the two side together again filling any void around the tang with epoxy. again pinning will improve this even if you can not pin threw the tang pin the two slabs together to strengthen against shear forces/separation. one can use some 1/4 stainless tubing to make a lanyard tube at the back and work as a pin. then shape handle
3) this will require three pieces two side prepared as above a second piece the same width or slightly thicker then the tang. I like to use g-10 or micarta for this. cut the shape of the tang in the micarta glue it to one side of the handle. sand micarta to same thickness as tang. the micarta must stay flat to prevent glue lines and unglyness. dry fit second side to in sure fit glue and pin all parts together shape handle.
I like to use g-flex epoxy from west systems it has a 75min work time and a grate holding strength. One can also use acu-glass, or 30 min epoxy I would not use 5 min epoxy as that it gives very little room for mistakes.
I use several (3) "c" clamps to hold every thing together while gluing and leave it in clamps over night.
All of the above epoxies will clean up with mineral spirits. I use an old tooth brush and some paper towels
the epoxy will run I set the knives on wax paper while it cures and wear gloves
If you have access to a belt or spindle sander they will speed the shaping process, if not use hand files the sand paper starting at 60grit move to 220. Finish with steel wool or Scotch bright pad. Round off any sharp corners to avoid hot spot.
I hope this helps let me know if I can or need to fill in any gaps in the info
I usually avoid such a long post, as that I am dyslexic and the written word is not my strong suit. If I need to clarify any thing above pleas let me know.