How to sew boxed corners
Cut squares half the depth you want.
Step by step
- Cut a square from both bottom corners of each panel: half the depth you want (5 cm for a 10 cm base).
- Sew sides and bottom, leaving the corner squares open.
- Pull the opening apart so side and bottom seams meet, one on top of the other.
- Sew straight across with the same seam allowance, then sew again for strength.
- Or pinch a sewn corner into a triangle and sew across where the line equals the depth.
Watch
2 Ways to Sew Box Corners (7:45)
By National Sewing Circle · Open on YouTube
Chosen from its title and channel: a 7-minute video from National Sewing Circle on the same topic as this guide. Embedded from YouTube with credit; we don't host it. It only loads when you press play.
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Sources
All checked 1 November 2026. We read these; we did not test the products ourselves.