[1] As soon as you start to sink, lay the pole on the surface of the quicksand.

[2] Do not struggle, and move slowly.

[3] Flop onto your back on top of the pole.

[4] Work the pole to a new position: under your hips, and at a right angle to your spine.
The pole will keep your hips from sinking, as you (slowly) pull out first one leg, and then the other.

[5] Take the shortest route to firmer ground, moving slowly.