Lets make the wing parts!
If building from plans, there is a solution to print ribs on paper, glue them (3M spray glue) on the balsa and carefully carve them with modelling knife.
The wing sections are build on the lower part of D box. It is a 1 mm balsa sheet.
I use some rubber bands that help me to hold parts on place until glue hardening. It is kind a funny aproach, but the end result is without flaws.
Wing after asembly under rubber bands pressure, with help of some balsa longerons to apply pressure to front and rear part of D tube sheeting.
Carving the wingtips from solid block of balsa.