You know what the perfect project is to practice straight-line sewing on the machine? Making some fancy schmancy cloth napkins! You get to practice sewing around the edge with a nice, straight, 1/4 inch seam allowance, and then you get to go around the edge again with a topstitch. So here's a free pattern for you.
If you want to get really fancy you can embroider on one of the squares of fabric before you sew them together. Maybe an initial? Or a flower? Or a small beetle? Draw whatever you like right on the fabric and then choose an outline stitch and stitch over your drawing.
We have a big stack of colorful napkins in our house and everyone has their own favorites. This is a great way to use up random bits of favorite fabrics.
I'm on a mission to teach people to sew, quilt, and embroider. I design patterns especially for beginners and I never release a pattern until I have videos teaching you every skill you'll need to complete the project. Have fun!