There are numerous methods of doing this, just ask google - inlays in walking sticks. In the UK it is a common practice to create the well/aperture for the inlay and then cast in using clear cold cast resin which is formed higher than the surface of the cane by making a plasticine reservoior round the aperture, when set it can then be taken down to surface and polished. The two main areas for this is the open end of a cowhorn handle and setting something in the coronet area of a antler handle.