With the three boards for your panel cut and the edges jointed, the next step is to glue up the boards, clamp them and set them aside to dry.
After determining the order of the boards that will look the best (based on color and grain patterns) in the panel, place a thin layer of woodworking glue on one edge of each of the joints and align the boards in a pair of woodworking clamps as shown in the image above. Tighten the clamps just enough to tighten the joints but not so tightly that the glue squeezes out of the joints. Be sure to immediately clean off any glue that does squeeze out of the joints.
Set the assembly aside to allow the glue to dry for the amount of time recommended on the glue's label.