Here's another way......
Step 1) Make both the inner and outer stem (yes, I used an inner stem on this boat. The extra 8 ounces of weight and strength it adds allows me to use my boat as a ram to be used on tubers and inner stemless canoes. Hear that POGO???
) In this case I have 10 pieces of 1/8 inch thick ash glued together with wood glue. Piece number 5, in the middle has no glue on one side. I put duct tape on it instead so it doesn't stick to its neighbor. Once everything dries I just give the bundle a good whack and it separates, leaving two pieces, an inner and outer stem.
Step 2) Shape inner stem with whatever tools you please. I like a beltsander. Then start a strippin'
Step 3) Use tool of choice to shape the mating surface. Like Gerald, I use a chisel on the very top, or the very botton, depending on how you look at things. I like a nice low angle block plane for the rest.
Step 4) Screw on outer stem to hold it while it dries. I used silica thickened epoxy because of the desirable gap filling characteristics.
Step 5) Remove screws, fill in holes with thickened epoxy, then once the epoxy dries, shape to taste! I used anything and everything short of a chainsaw to hog off all the extra wood.
All in all, I like Gerald's method better. I used that technique on my first boat.
But some may find this alternate method to their liking. So now, everyone knows two ways to skin a cat......