Most yarn holders my wife found were vertical and she wanted one that was horizontal so she asked me to design one. Very simple design.

You print out the base, and two side pieces and snap them together. The inner spool is meant to protect the ball of yarn and spin on the 3/8 inch dowels (sold separately). I used 12 inch dowels and just cut them to length.

For the print I used PLA with 4 perimeters for strength and 20% infill (base and side pieces).

For the inner spool I printed it vertically with a brim, 15% infill and 2 perimeters and that seemed to work well.