NOTE: Your printed fins and location of the spin tabs won't be the same as pictured below.
This is the first build before corrections were made to the PDF. Your model fin color and spin tab position will be correct. The following posts can still be used to make the model.
Cut and separate the fins.
Leave a 1/4" wide border around all sides.
For now, notice only the spinneron side trailing edge is cut out on the ink border.
After making the embossed leading edge from the last post -
Lightly fold down the embossed leading edge line.
Burnish the fold flat and sharp with the back end of a Sharpie or other smooth, round dowel.
Apply glue stick to both inner sides of the fin skin.
Don't apply any glue to the tab in the area shown.
Set the skins over the cereal cardboard straight edge cut earlier.
Be sure the skin fold leading edge is all the way down onto the cardboard edge.
Place the fins in a heavy book to dry.