Set up by placing a mat on the floor and loading up a barbell with the weight you want to use. Sit on the floor with the barbell on your thighs. Grasp the barbell with a wider than shoulder-width overhand grip and lay back on the floor. Alternatively, lay back on the floor and have a training partner pass you the barbell. Slowly lower the barbell down until your upper arms are almost resting on the floor. Pause, then slowly raise the barbell back up without lockout out at the elbows. Repeat for desired reps.
When lowering the bar you need to stop before your arms are resting on the floor. This keeps the stress on the pectoral muscles and doesn't allow you to rest mid-set.