To give yourself the best chance for blocks that lie flat and smooth, consider the fabric grainline when positioning your patches for cutting.
Wherever possible, plan to have the fabric’s lengthwise grain (along the selvedge) or crosswise grain (from selvedge to selvedge) fall along the outer edges of each section in the unit, block, or quilt. This eliminates possible distortion in the block.
Watch Jinny’s two-minute video for a quick explanation of grainline and some tips when rotary cutting patches.