1. Measure and Mark:
   • Take precise measurements of the area you intend to cover.
   • Using a ruler, measure the height of the sides. For instance, if it’s 8 inches thick, mark dots at the 8-centimeter position in the lower left corner of your fabric.
2. Create a Square:
   • Connect the marked dots with pencil lines to form a square.
   • Cut out the square using fabric scissors.
3. Fold and Sew:
   • Fold the two edges of the square underneath and sew them together using a sewing machine, both right and wrong sides. Trim excess fabric, maintaining a distance of about 0.5 cm from the edge.
   • Finish the fabric under the sewing machine by folding the corners over themselves half a centimeter twice, creating a corner.
4. Sew the Small Triangle:
   • The small square obtained earlier needs to be sewn under the machine, folding the ends to form a small triangle. Leave a small opening unstitched.
   • Place the triangle under the corner obtained earlier, and sew the ensemble under the machine. The small triangle will align with the corner vertex.
5. Final Touch:
   • One side of the small triangle will fall on each side of the corner, making the square obtained previously the base of your corner.
   • This technique is ideal for sewing sheets, tablecloths, sofa covers, etc., particularly for fabrics covering items with corners.

Once you master this technique, sewing corners becomes a straightforward task. Even if you don’t have a sewing machine, you can still proceed by hand, albeit with a bit more time and patience.