The Beachstart is the next level above the uphaul. It's alot more easier to launch yourself on smaller gear this way than uphauling the damn thing all the time.
Notice in the photo above, you should not be standing directly behind the board. Instead the board should be more towards the side of your thigh. The key to the beachstart is angle and position.
On your first try it might be easier to hold onto the mast for better control of the sail. Position the board a little downwind, but not too much and sheet out your back hand to keep the gap open. You'll feel the wind will tug on the sail and even more so when you pull your back hand in a bit.
Start in water over the knees to avoid sinking the tail and digging the fin. Begin with your back foot first, you can even place it on the board for a while just to get the feel and control of it before launching.
The next part is the sweep. You'll need to pull the board and sail towards you as you step on, then extending your arms above your head as if you are hanging. This will make your weight (through the sail) put pressure onto the mast base at the center of the board, the wind will also help you at this point.
As you get onto the board, point your front foot more toward the nose of the board, you should be looking forward with your sail slightly sheeted out. This will put you into a position for better balance and you'll be in a stance that's ready to sheet in and bear away.