Insert the 3 x Misumi LM8UU bushings to the Y carriage bearing holders.

Y carriage bearing holders are not directional. There are two tiny bumps inside the holders to hold the bearings in place.

Before assembling the bearing holders ensure that the hole in the middle of the y carriage is aligned to left.

Use 2 x M3x14 screws for each bearing housing.

Use 2 x M3 Hex Nuts in order to tighten the screws.

Y axis belt holder should be faced to two bearings on the left.

Use 2 x M3x14 screws to fasten the belt carriage as seen in the picutre. Holes on the Y carriage for the belt carriage are tapped and you don't have to use nuts to fasten them.