The design as-is is made to be cut out of 1/8" acrylic or wood.

You'll need to cut the file twice- once for each half of the reel.

After cutting, do not discard the internal remnant pieces. You'll need them to help with assembly.

To assemble, remove any paper, stickers, or other things from the cut pieces (in the case of paper-backed acrylic, you may do this before cutting, but that may result in soot on your workpiece).

Lay one of the rings on a flat surface that you don't mind potentially marring or staining. Place the internal remnant (in the case of the 150mm piece, it'll be the circle with all the little cross-braces cut out of it; for the 200mm piece, it will be a ring about about 5mm thick) inside the hole. This will help hold the cross-braces in place while you cement them.

Place some, but not all, of the cross-braces in the notches cut along the rim of the piece. Once a suitable number are in place (perhaps 1/4 of them; maybe less, in the case of the 200mm piece), gently lower the top piece onto the cross-braces. It may help to drop the second internal remnant piece in as well, to provide extra support. Then, go back and add the additional ribs in.

Once the ribs are spanning the gap and supporting the top piece, cement them in place. The choice of adhesive is up to the maker; for acrylic, a plastic weld type is the best choice. Allow the rib joints on the top piece to cure before flipping the piece and cementing the bottom joints.

Caveat creator: so far, I've only assembled one of these- a 150mm version out of 1/8" acrylic. I've not taken it flying yet. You may find it useful to soften the edges a bit by sanding to avoid abrading your line, and if it fails, it will likely fail by collapse of the ribs.