Satin stitch is many straight stitches close together. This can give a solid block of colour and create texture in your project.
Work satin stitch by starting in the widest part of the design and working outwards keeping your stitches close together. Then go back and complete the other part of the design in a similar way. If you are stitching an even shape like a square then it’s OK to complete the design from one side to the other.