FlexRC Pico Core is very easy to assemble, just follow the steps before and your racing drone will be ready in just a few minutes.
Solder battery connector to ESC
Cut off red and black wires
Solder black and red wires to power pads
Install nylon hardware
If hardware does not fit well, then use silicone washers to prevent damage to components. You can also slightly shave off excessive material from nylon standoffs which prevents them from fitting well.