When I was building my enclosure, i chose to use AcE Krystal's design for the fillament slot, with mind of having two spools at the ready everytime. But only as i had two sets already printed, i noticed that i would much more appreciated single long slot, rather than two separate ones.
I frankensteined my prints into one wide slot using a hacksaw and some superglue, and it works, but later i took time to re-model the files for printing for everyone to use.
This is the maximum size that should fit on the MK3S's bed, rotate 37°.
The author remixed this model.
Two instances connected to form approx. double width slot (for two spools side by side)