There are two easy hacks on how to finish slits on knit garments here to enlighten you.
1. Overlock the side edges of the garment pieces with the right side of the fabric facing up. Press the seams.
- Place the pieces right sides together and stitch the side seam all the way down to the slit. Backstitch at the slit notch. Press the seam allowances open.
- Finish the corners. To do so, fold the slit seam allowances to the right side of the garment and pin in place. Stitch along the hemline at 2 cm (3/4”) from the bottom edge.
- If necessary, trim the seam allowances to reduce bulk. Turn the corners right side out and press.
- Sew a П-shaped line at 7−8 mm (just over 1/4”) from the edge all along the slit, securing the seam allowances in place.
- Finish the hem on a coverstitch machine or using a stretch twin needle on a regular sewing machine.
When cutting the garment pieces, add the following seam allowances:
- to the side edge above the slit notch — 7 mm (just over 1/4");
- to the side edge below the slit notch (along the slit) — 1 cm (3/8”).
Join the slit extension and the side seam allowance with a smooth curved line.
- to the bottom edge — 7 mm (just over 1/4").
Interface the slit extension with straight-grain fusible stay tape.
- Overlock the slit extension edges with the right side of the fabric facing up.
- Place the garment pieces right sides together and stitch the side seams on the overlocker. At 1.5 cm (5/8”) from the slit, start pivoting gradually to join the stitching lines.
- Stitch on a regular sewing machine from where you started pivoting and down to the slit notch.
- Press the side seam allowance towards the back. Press the slit seam allowances open.
- Fold the waistband piece in half lengthwise right sides together and stitch the side seams. Trim the seam allowances at the corners and turn the piece right side out. Press the waistband.
- Place the waistband right sides together with the garment. Match the waistband’s short edges with the slit foldlines. Pin all along the bottom edge of the garment.
- Finish the corners. To do so, fold the slit seam allowance over the waistband and pin in place. Stitch the pieces together on an overlocker with the waistband piece facing up.
- Turn the corners right side out and press the slit.
- With a single continuous stitching line, topstitch all along the waistband, securing the seam allowances to the garment, and along the slit edges, pivoting at the corners.
- Press the seam.
Choose any you like.
More useful sewing tips are here: