Objective: Sew a complete, sellable small item — a lined fabric coaster — to practice seam allowance, pivoting corners, turning right-side-out, and topstitching on the Janome MC6650.
A coaster is the ideal first project because it uses every core skill you have learned on a tiny scale, so mistakes are cheap and fast to fix. You will sew two squares right sides together, leave a gap, turn it out, and topstitch to close. Three MC6650 features make this clean and repeatable. First, set the needle-stop-down position (the needle-up/down button) so the machine stops with the needle in the fabric — this locks your work in place at every corner so pivots stay sharp. Second, use the engraved seam-allowance lines on the needle plate; line the fabric edge along the 1/4" (6mm) mark for an even border. Third, use the automatic lockstitch or a short reverse at the start and end of each seam so threads don't unravel — important for a product someone will wash. Keep stitch length around 2.4-2.8mm for a strong, tidy straight seam. Leave a 2" turning gap on one side; after turning, press flat and topstitch about 1/8" from the edge all the way around, which both closes the gap and gives a professional finished look. The start/stop button lets you sew slowly without the foot pedal for maximum control on short seams.
Try it: Cut two 5" x 5" squares of quilting cotton. Place them right sides together and pin on all four sides, marking a 2" gap on one side. Set the MC6650 to straight stitch, needle-stop-down, stitch length 2.5mm. Align the fabric edge to the 1/4" guide. Lockstitch, then sew down one side; at each corner stop with the needle down, lift the foot, pivot 90 degrees, lower the foot, and continue — stopping and backstitching at both sides of your 2" gap. Trim the four corners diagonally (don't cut the stitches). Turn right-side-out through the gap, push corners out with a blunt tool, and press flat. Topstitch 1/8" from the edge all the way around, folding the gap's raw edges inward as you pass. Inspect: corners square, seams even, no puckers.