As narnianquilter wrote, the picture is made of blocks that are oversewed with fancy stitches.
Or you can definitely make it in a truly crazy patch way and it would be great. The only special ruler I think you would need is a 1/4" one so you can trim after sewing each new material on to what you already have. Mine has a lip so it stays put.
Crazy piecing is the only time I have put the iron near my sewing machine. Then I put on a timer so I wouldn't sit too long. It was fun.