Having completed both wing halves, sand the inboard trailing edges, the spars and the leading edges flush with the center ribs, which are canted at the proper dihedral angle. Then epoxy the wing halves together at the center and reinforce the joint with a strip of nylon tape. Temporarily mount them with masking tape so that you can sand the balsa blocks that form the wingtips to the proper shape. I first traced the pattern of the tip rib on each block and then used a band saw to rough-shape them. I used a razor knife to cut out the servo well in the wing center section and a razor saw to provide clearance for the servos in the two center ribs.
Right triangles keep the formers true and vertical while the glue sets.
Clips or clothespins are a great help for holding the aft turtle-deck sheet in place on the center stringer. When one side is secure, masking tape will hold the other side to complete the job. At this point, I usually assemble the airplane to see what the bare bones look like. When they look good, as in this case, I am eager to move on to covering. Because it seems to go more easily, I always cover the stab and fin and hinge the rudder and elevators before joining them to the fuselage.