Insufficient seam allowance cut

Pattern pieces that hang crookedly or twist once sewn were likely cut without aligning the grainline to the fabric's lengthwise threads. Measure the grainline arrow from the selvedge at both ends before pinning down.

Multi-size patterns nested together make it easy to accidentally follow a neighboring size's line partway around a piece. Trace or highlight the chosen size clearly before cutting, checking closely at every curve.

Pattern pieces ending up slightly distorted despite careful layout often come from fabric sliding under the pattern weights or shears as you cut. Use a rotary cutter with a mat, or weight the pattern heavily.

Seams that won't align smoothly, bunching at one end, usually trace to notches cut wrong or omitted entirely. Cut notches outward from the seamline as small triangles, matching the pattern exactly, and never skip them.

A piece cut with its markings or nap direction inverted usually happens when the pattern was flipped without checking the layout diagram. Always follow the diagram exactly and keep directional details facing one way.