To avoid printing support material, the spool holder and bearing mount are printed separately which means they'll have to be either glued or fastened together. This CAD explosion shows how the bottom base holds the outer ring of the bearing. The open features produce less material meaning less print time.
Start by joining the mount and spool holder together with the bottom surfaces mating. Then line up the mounting holes and insert five M3 x 5mm flat head Phillips machine screws. Fasten until fully tightened. The spool holder has chamfered holes to allow the head of the screws to be flush.
Grab the ball bearing and press fit the inner ring into the shaft of the 3d printed holder mount part. It ought to have a tight fit so it shouldn't be loose. If it is, the diameter of the feature will need to be adjusted in cat – Or update the slice settings with a horizontal compensation offset.
Place the 3d printed bottom base over the outer ring of the ball bearing. Firmly press the two parts together until the ball bearing is fully fitted over the outer ring of the ball bearing. The two parts should freely spin independently from each other.