Caution: Avoid using abrassive papers, because remaining abrassives inside the saya can damage the blade
Actually magnolia wood or similar is used for shira saya but this was not available.
Either you saw one piece lenghtwise (traditional) or you can use two pieces with half thickness (wood grain is then interrupted).

The shape of the saya with handle is marked on the boards and cut out. Handle and scabbard should then be trenched.
In both pieces the shape of the blade is chiseled. The blade should not touch the wood; it is held only by the habaki.
The scabbard mouth shall fit exactly the habaki. The habaki must not have play and should keep the blade safe.
The tsuka halves are chiseled in the same manner fitting the tang.
Is everything ready both halves can be glued together. If you want to split the scabbard later for cleaning reasons use traditional boiled rice paste instead of wood glue.
The hole for the pin was strenghten with a piece of bamboo.
A rectangular pice of Bamboo was prepared and a fitting hole was carved in the handle using small cutters.
Finally the piece was glued in.
The last step is shaping the saya with files and planers and polishing the surface.
The wood was only oiled and not stained.
The finished shira saya!