OK check out Spadtothebone.com as recomended before. Both flute directions have been used depending on the model. Flutes going chord wise arch better for the wing top curvature. A piece of span wise coro is often inserted as the aileron so the flute can be cut to make the aileron hinge...just depends on the bird.
Coro weight can be an issue, however birds in the larger 40 and up size can be made with resonable weights. For example the 40 size spad trainers are just fine weight wise, ( Spadet and Debonair) I would recomend either as a first plane.
Wing folding without warping is an art and is best done with a spare set of hands. So call your flyin buddy and "eat the cost of a pizza" ...
save the box!
used signs are more fun, especially politcal signage!!!