The setup was reasonably simple: I set a 5 second delay, to allow me to get ready. Once the camera started taking pictures (continuous shooting, about 7 frames per second), I tossed the ball into the air, and ran to catch it. I omitted a couple of frames at the end of the sequence, so that I didn't "overlap" with myself. (Hence the small gap in the ball's trajectory.)
Taken with Canon 70D, Tripod Mounted, Manual Mode. Used a separate intervalometer to control the delay and shutter: Configured the timer to wait 5 seconds, then hold the shutter open for 2 seconds. However, since the camera was set to continuous shooting, it took ~14 consecutive frames during those 2 seconds, which captured the action.
Used 7 of the captured photos / frames for the final shot. ISO 200, 12mm, f/5.6, 1/400s. I pre-processed the original RAW images in Lightroom, and converted to smaller JPEG images. Imported the JPEG images in Photoshop, each in a separate layer. Then used layer masks to select just the "action" in each shot, allowing all to blend together.