I based my design around these, with a modification to have a stronger main spar that also helps produce the curvature needed. One of the pieces of foam i purchased for the project was a half inch thick foamboard, and i used 2 inch wide cuts for the structure of each wing:

It turned out I had to trim a chamfer along the top edge of the spar to lower the overall camber of the wing (it was way to aggressive before). Using hot glue I glued the spar to the top panel of the wing, bent the upper surface down, and glued it to the trailing edge, similar to the tutorial.

Each wing had its respective modifications needed. The forward wing had the flaps trimmed on the inside to accommodate the fuselage, and the rear wing had the entire midsection removed to allow it to snugly fit along the bottom of the fuselage.

As it turns out hot glue and the water repellent coating on the foam dont mix well, so for mounting the servos, which need strong adhesion to counteract the reaction forces when moving the flaps, i cut out the coating around there.