In this knitting tutorial, I am showing you how to close the side seams of your sweater with the mattress stitch - to achieve the neatest result possible!
Sometimes, it's useful to wash and block the garment first before using the mattress stitch, especially when the fabric stretches a lot after washing and blocking. This applies especially when using super wash yarn or when you are not sure how your knitting tension will behave during washing and blocking AND the knitting process.
Furthermore, I recommend to lay the garment flat when working the mattress stitch.
Happy knitting!