Just had a go and it says "Unfortunately you cannot place an order without a hard disk drive or SSD drive" that's a bummer as i have got 2 M2's already.So you'd be supplying just the GPU and RAM?
I think the least you get away with would be (as they have to be able to test it):
- Case
- Motherboard
- CPU (as long as it's got an iGPU)
- Cooler
- Power Supply
- RAM (but you'd just buy the lowest speed/size available - 8GB of DDR5 4800MHz for c.£29)