The most fundamental quilt block design is the plain square. It actually doesn’t even have to be square, rectangles work just as well (even octogons).
Just sewing together different square blocks of various fabrics can result in wonderful color patterns. But to start the conversation about plain square blocks we have to talk about the ultimate plain quilt block, whole cloth quilts.
These are very easy to create, but not so easy to complete. Because of the lack of other design, more focus is on the quilting. When done well, whole cloth quilts are spectacular.
Because they are made of one piece of fabric, I am including them in my category of plain quilt blocks. They are, however, a very special type of plain block.