So, w1nd6urfa is surprised that the wing is built without supporting everything firmly. No tabs from every rib to a flat building table, or rods supporting every rib.
People have built smaller laser cut models practically in their hands: no support. And the result is straight.
Maybe laser cut parts with good tolerances help you get straight structures. And jigs or tabs are not needed?
If your parts are perfect, a jig or table that is NOT perfect could give a twisted structure.
edit:
below, fokke shows that the ribs have tabs (legs).
Flat surface is needed
