How do you slid the foot while doing ollie?

Well you have to position your feet right and also jump forward with the board.
your back foot MUST be on the tail slightly off and your front , just before the bolts, then crouch, pop the tail, scrape your front foot up the board, jump forward and lift your legs so your knees touch your stomach.

the grip tape may need replacing, also use GOOD skate shoes e.g..... DC, etnies, globes, etc.

Hope This Helps :D

By Chaz