After your fingers have recovered from cutting the ventilation slots on B.3.4, B.3.5, B.2.3 and B.2.4 glue, B.2.3 on top of B.3.5 and B.2.4 on top of B.3.4. align all edges. Make sure that the vents lineup. Sand down any misalignment.
Next glue the B.2.3-B.3.5 assembly onto B.4.1, and B.2.4-B.3.4 on to B.4.4. Align the parts as indicated by the red arrows
The pattern and the protective film can be removed from the back of each assembly.
Glue B.0.9 on to B.1.10 and B.0.10 on to B.1.11. Align all edges and make sure the vents line up. Sand down any misalignment.