While 100% cotton sofa fabric is naturally flexible to some extent, you can take certain steps to improve its flexibility and ensure it remains comfortable for seating. Here are some tips:

Choose the Right Weave: Cotton fabric comes in various weaves, each with different characteristics. Fabrics with looser weaves or those made using techniques like jersey knitting tend to have more flexibility and stretch. Consider selecting a cotton fabric with a weave that aligns with your desired level of flexibility.

Use a Fabric Softener: Fabric softeners can help relax cotton fibers, making them feel softer and more pliable. Be sure to follow the manufacturer's instructions when using fabric softeners during the washing process.

Pre-Wash the Fabric: If you're working with raw cotton fabric for upholstery, consider pre-washing it before sewing or covering your sofa. This can help remove any sizing or stiffness that might be present in the fabric.

Tumble Dry with Low Heat: After washing your cotton sofa covers or cushions, tumble dry them on low heat with a few clean tennis balls or dryer balls. This can help fluff up the fibers and enhance the fabric's flexibility.

Regularly Rotate and Fluff: To maintain the flexibility and even wear of your cotton sofa cushions, rotate and fluff them regularly. This helps distribute pressure and ensures that the fabric remains pliable and comfortable.

Consider Fabric Blends: If you desire a high level of flexibility in your sofa fabric, you might opt for cotton blends. Fabrics that combine cotton with spandex, elastane, or other stretchy materials can offer greater flexibility and elasticity.

Professional Upholstery Techniques: If you're reupholstering your sofa, consider consulting with a professional upholsterer. They can use techniques and materials to ensure the fabric maintains its flexibility while being securely attached to the sofa frame.

Regular Maintenance: Proper care and maintenance, such as routine cleaning and protection from direct sunlight, can help preserve the flexibility and appearance of your cotton sofa fabric over time.

Use Cushion Inserts: Consider using cushion inserts or fillers that provide additional flexibility and comfort. High-quality cushion inserts can enhance the overall comfort of your sofa.