If I didn't have any scraps, I'd buy an assortment of fat quarters and cut them in various width strips 2", 3", etc. I would start with a piece in the middle of my block in either a triangle shape or as someone has suggested a 5 sided piece in the shape of a house and then just start sewing onto that using a muslin backing. You can also cut squares from old sheets or even some ugly material you wouldn't put on a quilt top. By using strips, you can just use whatever length you need, cut it to size, then use it again where ever it will fit. When you get your foundation fabric covered - use a ruler & rotary cutter and square up. There you have a block. I like to put sashing between my blocks so they don't all run together.