U3-and-P3 is a super simple pattern. By varying the row repetitions and warping configurations, you can achieve a number of looks.
U3-and-P3 with L1-3/4 warping configuration
BASIC INSTRUCTIONS
R1: P
R2: P2, (U3, P3) x 4, U3, P2
Repeat R1 and R2, ending R15-16: P
Variation (shown in the photo and on the chart) — the extra plain weave row at the top (R15) has been eliminated and the pattern is centered on the square.