I purchased a whittling knife blade last summer and designed a handle amd sheath from one single piece of wood. Using coping saws to refine the shape of the handle and sanding it down to a smooth finish, I first drilled a hole through the wood and glued in the blade. To create the sheath I split the wood and chiselled out the shape on the blade, before gluing it and sanding it to create a seamless finish between the handle and sheath, that the blade disappears into. I focused on the ergonomics of the handle for this knife as I wanted it to be comfortable for the user when wood carving over long periods.