Usual footprint and profile of P2PPCB naked style keyboards

P2PPCB platform is mainly for rapid prototyping, so the products are usually naked style like starter kits.

The design of P2PPCB doesn't much focus on smallness. If you need really small keyboards, the versatility of P2PPCB is unnecessary burden (however it is a good idea to make a prototype and verify the function and suitability before consuming much for smallness).

Although sometimes smallness matters.

Bespoke / handmade keyboards are (usually) covered style and elaborate thing, so the story is quite complex. Let's put that aside, I'd like to give you a rough estimate of common naked style keyboards.

Flat, 60% layout, 19 mm key pitch, Gateron Low Profile, Junana MX

Junana is for 17 mm pitch, but I guess that you are not familiar with 17 mm pitch keyboards (the footprint is really small), so I chose 19 mm pitch. 

P2PPCB is for 3D-shaped keyboards. But the example here is to show the limit of smallness.

The overall picture:

The design is an hour job and printable / assemblable actually. No elaborate thing but workable and reliable. P2PPCB adjustable foot kit provides tilt angle as you like.

The width is 297 mm, the depth (near to far) is 132 mm, and the height is 19 mm. The 19 mm is competitive value as a mechanical keyboard.