Might be a repost, but here goes...
An easy way to make levels all by yourself, with minimum requirements to gear. You make roughly a level per run up until level 60, but can continue doing this all the way to level 70.
See the video below - it's only 4 minutes, or read on for a short guide:
1) Create game in normal mode, Act 1, The Fallen Star, Rumford at the gates.
2) Exit the city gate, breach the barricade and proceed to kill 2 of the 3 wretched mothers for the bonus objective.
3) Leave the game.
4) Change difficulty to Torment 6 and resume game.
5) Exit the city gate, and a wretched mother will be waiting for you.
6) Kite her inside the city, and she will die instantly. You will receive XP and gold for completing the bonus objective on Torment 6.
7) Repeat as much as you want.
I call it "The Rumford Rumble" - have fun!