Before you get started, make sure you know what materials will safely contain the rabbits. You could always start by looking through your leftover materials from other homestead projects.
To make sure you give your animals enough space, plan to give each rabbit an area roughly four times its physical size. This will give it enough room to freely move around inside the cage. For average rabbits, this would equate to between 4 - 5 square feet of space per animal.
If you have some untreated 2x4 and 4x4 lumber, these will be ideal for the framing and supports. Use the 2x4 pieces for framing a square box to the dimensions you’ve settled on for your number of rabbits.