First, follow the instructions from JLC for exporting Gerber's from KiCad 6. This works pretty much the same in KiCad 7.

Next, navigate to the front page of JLC and click “Order Now”. Then upload your Gerber's as a zip file to JLC in the “Add gerbers now” button.

Follow the specifications below when configuring.

Defaults for Flight Boards

Delivery Format 1 PCB
Material TG155
Surface Finish ENIG
Gold Thickness 1U”
Outer Copper Weight 1oz
Inner Copper Weight 0.5oz
Via Covering Epoxy Filled & Capped

Specifications for Individual Boards:

PyCubed Mainboard

Standard PCBA

Layers 4
Thickness 1.6 mm
Impedance Control Yes, JLC04161H-7628 stackup

PyCubed Battery Board

Standard PCBA

Layers 2
Thickness 1.6mm
Impedance Control No

Solar Panel Boards

Advanced PCBA

Layers 6
Thickness 0.8mm
Impedance Control Yes (±Z only JLC-060811-3313 stackup)
Outer Copper Weight 1 oz
Inner Copper Weight 1 oz

Coil Panel Boards

Advanced PCBA

Layers 6
Thickness 0.8mm
Impedance Control No
Outer Copper Weight 1 oz
Inner Copper Weight 1 oz