How it works
The height is shared equally between the drawers. Each front laps over the cupboard's sides, less the gap round it. Behind it, the box is as wide as the inside of the cupboard less room for the runners each side, a little lower than its front, and as deep as the longest runner that fits.
The box's sides run its full depth with the front and back between them, and the base sits in a groove all round. Change any of the numbers to match your runners and how you build.
For choosing runner lengths and how deep a drawer can be, see drawer runner lengths and drawer depth.
Questions
How long are the drawer runners?
The longest of the lengths you can buy that fits the depth inside the cupboard, less the gap behind the box. The box is made as deep as its runners.
How wide is the drawer box?
The width inside the cupboard less the runners' room each side: about 12.5 to 13 mm a side for most ball-bearing side runners, 1/2 inch for most American side-mount slides. Check your runners' instructions: they say exactly.
How high is the box?
Each drawer's share of the height, less how much lower the box is than its front, so the front covers it above and below and it slides without catching. 40 mm is a usual start.
How is the box put together?
Two sides as long as the runners, and a front and back that fit between them. The base sits in a groove all round, so it's cut that much bigger than the inside of the box each way. Fronts lap over the cupboard's sides, with a small gap round each one.
Is this the same as JoinerKit's drawers?
Yes. It's checked against the code that builds drawers in JoinerKit, where drawers can also go in a space under a shelf, sit behind doors or stand under a sloping ceiling, each with its own runner length.