This design solves all the basic necessities:

Fits almost every object with a flat top surface and printer frame when customized.


Can easily hold the weight of 1+ kg spools.

Fits between other spools if necessary.
In addition to above criteria, I've optimized for:

Print quality: Friction-less rolling is achieved by adding bearings, no pulling required by extruder stepper motor


Economic design: I've added holes in the guide to reduce material use and shorten print time without compromising strength. Since the guide has the longest printing time, I separated the guide from the brace. Just print multiple braces, and move the brace to the desired spot.


Ease of use: Just place the guide in the bracket, hang the spool on the guide, and off you go. If there happens to be another guide right next to the one you want to use, you needn't move it out of the way. You can place the spool on top of two guides.

Ease of printing: All objects are placed in such an orientation that requires the least amount of support…

Introducing TUSH - The Ultimate Spool Holder v.2. I was using a regular spool holder. Not the most convenient design, if you ask me, because It takes some time to replace the roll. Also, based on 608 bearings, It gives more than requested length of filament since there is no traction. That's why I designed this Ultimate Spool Holder. It is simple, easy, sexy and comfy.
For one spool holder you will need to print four pieces of this. Also, you will need four 608 bearings. Get the cheapest ones. They are available everywhere. This is press-fit design. Just press the bearings into the printed part, and voila, you have The Ultimate Spool Holder! Congratulations!
UPDATE: Version 2 uploaded
This is exactly the same TUSH. Just some fixes. Now Simplify3D ans slic3r should be happy with the model. Cheers!