Skip to 20:50 for final result.
03:42 Flap and Front part with velcro.
07:35 Back part with webbing.
11:24 Mounting the back with the flap.
13:30 Attaches the front.
17:15 Attaches the plastic to the ends of the webbing.

Made some changes/improvements from the second one i did.

Fabric Cordura 500D
Thread Bonded nylon 40S/TEX 70
Needle 110/18
Singer 331K5

I am a beginner so I do not claim that my way is the right/only way to do it.
But if you have constructive criticism, I would love to listen to it.