1”, 1 1/2”, and 2” Bias Tape Makers are designed by William Walter; The dirtyvalentine on Thingiverse.

The slot on the back is added by Homer Prints and printed by What's Your HP?.
Each tape maker is two pieces that fit together. The first piece creates the first fold and could be used by itself to aid in ironing or sewing. When added, the second piece provides another fold. We have found that cutting a slight point on the beginning of the fabric helps to get it started.
The slot on the back aids in feeding the cloth through the maker. Once the fabric is inserted in the end, use any pointed device to grab the fabric in the slot and pull it through the maker. Once in the maker, it will feed easily.

Thank you for this opportunity to help;
The staff at What's Your HP?

Instructions from the designer:
This device folds 1", 1.5" or 2" fabric (bias tape) into strings for protective masks. The first section is your typical bias tape folder that folds the outsides of the tape into the center of the bias tape. The second section follows the first section to fold the bias tape in half so it can be sewn. This device does not require ironing. The folded tape is fed directly into a sewing machine. This makes the creation of tie strings for protective masks extremely fast and easy. The two sections fit together to make a single device so both folds can be done at once.

The two sections are designed to come apart to make loading the bias tape easy. Note: the back of the fabric should face the side labeled "IN". Insert the fabric into the slot on the side labeled "IN" on the first section. (You can use a Bias Tape Loader or the slit on the bottom to push it through.) Grab the fabric from the side labeled "OUT" and pull it out about 4". Now insert the end of the fabric into the slot directly below the side labeled "IN" on the second section. Push the fabric out the side Labeled "OUT". Pull the fabric out and adjust the fold as necessary. Now connect the "OUT" side of
Section one into the "IN" side of section 2.

You are now ready to sew. Hold device in one hand and feed into sewing machine with other. Be very careful to lay out cloth strip so that there are no twists. If a twist enters the folding device it will mess up the fold and be hard to recover from. I have made many of these ties without issues so it's just something to be careful of.