The backpocket is for the battery recharger or for used batteries.
I printed it with a 0.6 nozzle volcano, 0.6 layer height, 2 perimeters (3 on a 0.4 nozzle), 5% hexagonal infill using Geeetech transparent PLA. I set my Prusa Mk3S to 200% speed and it printed ok
The author remixed this model.