Here is the explanation for Intarsia, another of my past hobbies.
Most intarsia projects are made from a simple pattern, such as an eagle, a dog or any other item you are fond of. The wood is chosen based on how it will appear on the pattern such as on dark or light areas, and sometimes painted ones. Woods are selected by color or grain, and are about ¾ inch thick for uniformity.
Each piece of the pattern is transferred to a piece of wood and is cut on a band saw or a scroll saw. It is important to do only one piece at a time to make sure there is a perfect fit between them. Even the most careful cut sometimes gets out of the pattern line. The pieces are then sanded on a drum or circular sander to give a rounded effect. The depth of the sanding is regulated by how it will fit into the finished design, giving it a three dimensional effect.
When I worked on a large piece, like a crane with slender legs, I mounted all the pieces on plywood or hardboard to give strength to the more delicate pieces. This is a fun hobby. It produces a finished project much quicker than the marquetry I have described in a previous post.