Yes, it definitely matters where you cut. Also the location on the plant matters as well. I tend to have more success when cutting on the lower portion of the mom, although success at the upper portion is possible too. Go to Walmart, get their jiffy pellet seed starting kit for $10. It comes with about 16 pellets, a tray and dome. Soak the pellets in water, wait for them to swell, give them a slight squeeze to remove excess liquid, definitely get some clonex or powder rooting hormone, dip the clone in either of the 2, insert in the pellet. Spray the dome and leaves, place dome back on the tray under a light but not directly. ( Make sure the light isn’t very strong ) Since you have a heating pad use it, better if you could control the temp. Wait at least 12-14 days, voila! Roots. Make sure you cut the tips of the leaves off to stop the plant from trying to use photosynthesis to grow, but instead focus on growing roots. Good luck.