Build a cardboard box that measures 2" x 3" x (Length of blade)
Make sure it's leakproof with vasaline or silicone caulk. Set the box upright. Mix and pour molding silcone into the mold to 1" before the top edge.
Then gently stick the blade(point-first) into the center of the silicone and hold it in place with duct tape. Let it cure completely. The cut open the mold on one side to remove to blade master. Duct-tape the mold closed and pour your resin.
That's the easiest way that I know of that works well.
It's not the least expensive, though. Mold silicone is not cheap. Expect to pay about $50-$75 for the amount you will need. Check with MonsterMakers for the silicone.
There are many other ways to do such a mold. But this is pretty much the fastest and simplest way to go.