I designed this boot stand to keep my boots stand straight. You will need to Print 1 "main" part and 2 "extension" parts for long boots. They snap together and keep in place very well. You can also just use the "main" for short boots if needed. I printed it with 2mm wall, 0.2 layer height, and 20% infill. Polymaker Matte Ice blue PLA : https://www.amazon.com/dp/B094FH3TRN/ref=cm_sw_r_as_gl_api_gl_i_HEQ2AN2X1N3B3HRYYS9Y?psc=1&linkCode=ml1&tag=yjdesign-20

Make sure you put them diagonally to fit the 220X220 mm build plate like the one on an Ender3.