When I make a birch bark puuko or Saami knife, I use the heavy bark and clean it off with a wire brush. Any loose paper needs to come off. What you have is like a sheet of hard leather - .10" to .13" thick. If very dry, it may split and fall apart, so soak it in water to make it soft for working and compressing if needed.
Bo Bergman's book on "knifemaking" is the authority book on Scandinavian knives. It is pricey, but worth every penny. Many libraries have it or can get it.
Start with cutting out rectangles of the bark. Make them a bit oversize. You can slot each piece stack on the knife tang, and do it in the classic style, or use the trick below. If you use the "stacked on the tang" method, you need to seal the handle, once that it is shaped. The classic way is to soak it in Linseed oil for several weeks and then let it cure over a few months. This works, but many other sealers work as well and are faster. Try using a thinned sanding sealer like woodcarvers use, or use thin CA. Apply several coats, and sand them down, repeating and sanding as needed until all fibers and pores are sealed. Then sand smooth and buff lightly.
Here is a tip/trick I posted about doing one a year ago:
A trick for making stacked birch bark or similar handles is to make a jig for assembly. Make the handle block up and treat it as you would do with a solid block of wood from there.
You punch a 1/4" hole in each square, (soak the bark to soften it if needed), slip the squares on a piece of 1/4" wood dowel, and compress the stack with a wood clamp that has a hole drilled in each jaw ( see below clamp directions). It is a good idea to put a 1/2" thick wooden block and a few layers of wax paper on each end of the stack to keep the handle from gluing to the clamp. Applying wax or white petroleum to the clamp is also smart. Let the bark dry under pressure for a week. Now,while still compressed, soak the stack with thin CA repeatedly until it will not absorb any more.This may take several days of soaking and letting absorb. Don't rush it and don't use accelerator. Take the assembly off the clamp, and rough sand to an oversize cylindrical handle shape, re-clamp and re-soak with CA. After the CA has had a few days to cure completely, drill out the dowel, shape the tang hole, and assemble on the knife. A final sealing with CA before the last sanding will leave a beautiful surface with all the birch bark grain character showing.
You can use a waxed, smooth, stainless steel rod instead of the dowel, and drive it out of the stack, but it can be a trick getting it out sometimes. The wooden dowel is easy to drill out, and works just fine.
I have used this same method to make a stacked handle for a wedding cake knife from cut up pieces of woman's great-grandmother's wedding dress, and another time used a pair of WW2 army boots to make a stacked leather handle for a knife the original boot wearer's great-grandson would take to the Mid-east.
It will work with any material that can be cut, stacked, and glued. Think - Yard sale elephant skin boots, old leather coats, exotic leather scraps,....let your imagination run wild. It is the side view of the stack that will be seen, so the current surface isn't an issue.
You can also make up a batch of handle blanks at one time, and leave the rough shaped cylinders on the dowels...ready for your next projects. This will greatly speed up making a batch of puuko's.
Using the same method with larger rectangular pieces of bark can provide the blocks for a classic puuko sheath.
The tool needed:
Every maker should get a large woodworking clamp ( the type with two screw handles) and modify it for gluing handles. First, disassemble the clamp, and cut a slot in the end of one jaw. The slot should be big enough to allow the ricaso of a hidden tang knife to sit in the slot. Next, drill a 3/8" hole opposite the slot ( in the other jaw). This will allow a stack of things to be compressed and/or glued up on the blade tang. The slot also is great for gluing up solid wood handles to the knife and clamping to allow a perfect ( no gaps) fit while the epoxy dries.
Now, drill another set of 3/8" holes just a bit back from the slot. These holes should align with each other. Use these to clamp up stack of things on a dowel or metal rod.
This clamp will become indispensable in making knives after you have it.
This is a tutorial I found on assembling a birch bark knife on the tang:
http://imageevent.com/paleoaleo/makingabirchbarkknifehandle?p=0&w=1&c=3&n=0&m=45&s=0&y=1&z=2&l=0
