I would like to ask you,
1. How did they make such clips?
2. Сan it be done only with pre-preg? or somehow with resin infusion?

Not the best picture but from zooming in they look like carbon.  So either cut out from flat sheet and bonded into place or what looks more likely, they were moulded that way around the mould flange/edges then cut to shape afterwards. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi
Looking the picture and I may be wrong, the distortion on the inside fabric reflections and levels, these clips are prefab and inserted into mold.
I guess they manufactured the outside skin by either prefab oven cure or injection and then laminated the clips into the stabilizing ( second ) inside layer hence the rough finish on the outer edge and fabric distortion
The inner side looks like a second lay-up oven cured
T