When piecing crazy quilting only the first patch is cut to shape, for the rest rectangular chunks of fabric are cut and trimmed off after the next patch is seamed over them, the shape of the patch being determined by the angle that later patches are added. The small bits that you trim off can be used by randomly stitching them together, straightening one edge and then using them as a single patch on the main block. As you become more proficient and understand how the piecing works you can economise on fabric by leaving the fabric in bigger chunks (I have trailed up to fat quarter sized chunks through the machine).
Cut the first patch of fabric to desired shape and size plus seam allowance. A five sided shape gives you a variety of angles to start with , but it can equally well be a four or three sided shape. This can be a good place to use a feature fabric, piece of embroidery or cross stitch, remember to add seam allowance. For a 30cm block start with a patch about the size of your hand.
Place this first patch right side up in the centre of your foundation fabric (fig. 1)...and then pull it a little off centre so that the block is irregular from the start.
Do not stitch or turn this first patch.
Take the second patch of fabric and place it right sides together along one edge of the first patch.
I don't do a lot of pinning but it can be handy to put a pin at the start and end of the seam (fig. 2), where you have 3 layers of fabric (the foundation, and 2 pieces of crazy fabric). Stitching past these points increases the chance of holes where you don't want them and any stitching past these points will have to be pulled out to trim the seams.
Stitch 6mm seam through all layers. You don't have to backstitch the ends as each end will be sewn over with a later seam.
Iron seam open. When ironing use the tip of the iron to push into the seam opening it out completely.
The third patch of fabric is placed right sides together along another edge of the first patch and across the second patch.
Trim seam (fig. 3) and iron. Each seam is trimmed if needed (to reduce bulk and minimise shadows showing through on the finished work), then flipped open and ironed.
Subsequent patches are placed right sides together where you want the seam to be, start by putting a patch on each edge of the first patch, then add them randomly (This is only a guide to get you started, I often go random from the start, it can mean that you will get long seams to piece, or a corner to fill but it makes for more variety of patch shapes). Note how each seam is a straight line which can run over several previous seams (fig. 4).
Continue adding patches until the base is covered (fig. 5). The finished work will have a variety of patch sizes from quite small to reasonably large.
Working on the back of the piece. Zig-zag, straight stitch or overlock close to the edge. Working on the back (where the grain is straight) will prevent the crazy patches stretching along the edges.