Notice the lines formed by the plys of the panel are smooth and even. Mate the two scarphed panels and check the fit. This looks fine. Before gluing the scarph, lay plastic on the surface beneath it. Also, tape the panels just back from where the scarphs meet.
Packaging tape works fine.
This will make it easier to remove epoxy that has squeezed out. When gluing the scarph, be sure to apply unthickened epoxy to both parts of the scarph first. Then apply epoxy thickened with colloidal silica to the joint, line up the panels, and stape or tack them together.