Experiment with left-over squares to see what you can turn them into. If you know the number of stitches on the diagonal, you can calculate the number of stitches to pick up along the edge of the square then knit in any direction you want.
This child's sweater started with twelve identical squares. Two strips of six were enough to form the length of the sweater but not wide enough.
The squares were stitched together and a row of stitches picked up on the white edge. The neck was left square so there was no shaping to do. The white pieces were knitted until the sweater was wide enough and a little extra added at each side for a lapped fastening at the neck.
The stitches for the sleeves were picked up from the navy sides of the squares. A neckband was added which pulled the neck into a more rounded shape.
The squares in the lower part of this waistcoat were originally intended for another project. I stitched them into a strip long enough to go right round the waistcoat then picked up stitches and knitted upwards and downwards.