The order for the bearing stack from the bottom is: shim, idler, shim, 2x 6mm spacer, shim

Thread the bearing stack onto the Cap Head Screw M5x40

Attach the M5 nut from the bottom, do not over tighten - it should be snug but should not prevent the idler from spinning

If you are having trouble getting the bearing stack into place, thread the bearing stack onto a thread or a thin wire, then pull the ends of the wire through the holes in the mount, from the inside out. The bearing stack will slide into place.