Making a complex orchestral instrument requires lots of practice. Skilled luthiers learn their trade over years of study, practicing long hours to learn how to build violins, cellos and other similar stringed instruments. The process can take weeks, but it breaks down into a few essential steps.
Carve the scroll and neck from a single piece of wood. Sand it and smooth it. Then drill holes for the pegs for the strings.
Bend and glue the rib pieces (usually six thin strips) around the form. Then fit and glue the lining pieces that go inside the ribs.
Cut the back and front pieces each from a separate piece of wood, using the completed rib assembly as a form. Hollow out the inside, adding a bass bar and the f holes to the front piece.
After making sure everything lines up, glue the ribs to the back piece. Remove the form after drying and attach the front piece.
Carve the mortise, which must be measured carefully to ensure a proper fit, to attach the neck piece. Then slide and glue the neck into place.
Varnish the body and neck of the cello. Then carefully attach the fittings (the saddle, nut, pegs, end pin--usually carved out of ebony--soundpost and bridge) before fitting the strings onto the cello.
Constructing a musical instrument like this is a lengthy project, which requires a luthier to set aside plenty of time. Before the cello is completely finished, it needs to be tuned by a professional musician.
Simple carpentry or woodworking skills (or even great carpentry skills) are not the same as being a skilled luthier. If you don't have someone experienced to show you what to do, trying to build a cello on your own will be a waste of your time and money.