1. Prepare Your Fabric and Pattern

• Check fabric stretch percentage against pattern requirements (typically 50-75% stretch).
• Layout pattern pieces on fabric with greatest stretch going horizontally around body.
• Use pattern weights instead of pins to avoid permanent holes in fabric.
• Cut with rotary cutter for clean edges that won’t snag or run.
• Transfer all markings with washable marker or tailor’s tacks.
• Cut lining pieces if required, typically for bottoms and bust areas.

2. Set Up Your Machine

• Install stretch or ballpoint needle appropriate for fabric weight.
• Thread machine with quality polyester thread in needle and bobbin.
• Select appropriate stretch stitch: narrow zigzag (width 1.5, length 2.5), triple stretch stitch, or lightning bolt stitch.
• Reduce presser foot pressure if possible on your machine.
• Test stitches on fabric scraps, checking stretch and recovery.
• For serger: use 4-thread overlock with polyester or woolly nylon thread.

3. Construct Main Seams

• Pin pieces with ballpoint pins perpendicular to seam line.
• For lined pieces, baste lining to wrong side of main fabric within seam allowance.
• Sew seams using 3/8 in seam allowance unless pattern specifies differently.
• Avoid stretching fabric while sewing; let feed dogs do the work.
• For crotch seams, sew twice for durability or reinforce with clear elastic.
• Press seams gently with low heat, using pressing cloth if needed.
• Trim seam allowances to 1/4 in if using serger finish.

4. Apply Clear Elastic to Structural Seams

• Cut clear elastic to 75-80% of seam measurement.
• Position elastic on wrong side along seam line.
• Using zigzag stitch, sew elastic while gently stretching to match fabric length.
• This technique works for shoulder seams, leg openings, and waistbands.
• Ensure elastic lays flat without twisting.

5. Attach Swimwear Elastic to Edges

• Measure body openings and cut elastic to 80-85% of opening measurement.
• Quarter-mark both elastic and fabric opening with pins or marks.
• Pin elastic to wrong side of fabric, matching quarter marks.
• Using 3-step zigzag or specialized elastic stitch, sew elastic while stretching between pins.
• Overlap elastic ends by 1/2 in and secure with straight stitches.
• Fold elastic to inside and topstitch with twin needle or zigzag for professional finish.

6. Create Leg and Armhole Openings

• Apply elastic using above method or use fold-over elastic technique.
• For fold-over elastic: position center of elastic over raw edge.
• Sew along inside edge while stretching elastic slightly.
• Fold elastic over to encase raw edge and stitch again from right side.
• Check that elastic lays flat and doesn’t create puckers.

7. Add Closures and Hardware

• Reinforce areas where hardware will attach with interfacing or extra fabric layer.
• Attach hooks and eyes with sturdy hand stitching or bar tacks.
• Install bra closures according to manufacturer instructions.
• Add sliders and rings before closing seams where applicable.
• Test all closures for security and comfort against skin.

8. Finish Hems and Final Details

• Hem bottom edges with twin needle for stretch and professional appearance.
• Alternative: use coverstitch machine or narrow zigzag hem.
• Trim all thread tails and check for secure stitching.
• Try on suit and check fit, making adjustments as needed.
• Rinse suit in cool water to remove any markings and test construction.