Jam the inside end in far enough and hard enough that it will not slip back out. Carefully start unwrapping the rim tubes. It helps to squash the circular shape to a very ellipical shape while doing this. Unwrap about two layers as shown at top. Where you have unwrapped the rim tube, insert the tab on the inside end of one of the earpiece tabs.
Re-wrap the end of the rim around tightly to capture the tab from the earpiece tube.
Restoring the rim tube to a circular shape after re-wrapping will help prevent this from unwrapping again. You now have two complementary sides. Slip the other rim over the long end of the flat bill, making sure the earpiece is in the right orientation. Fold the end of the flat bill so that it now forms a right angle to the previous wraps. If not, do not continue.