How do you take a decent photosphere? My shots are always distorted and horrifying.

What I have been doing is:
  1. Making sure the subject(s) stays still.
  2. Aiming the phone at the first 'shot spot'.
  3. Spinning 360 degrees steadily while making sure my feet stays on the same spot (I even use stones to mark the position or a floor tile as a reference point) and my arms stay steady.
  4. Repeat for the upper and lower shot spots.

Yet the results have always been messed up. They're distorted, blurred at some areas, or disproportionate.