All prices in stops, limits, targets, indicators etc. are generally Ask prices - no matter if it's for a long or short order. If you want to use the Bid price instead, you must subtract resp. add the spread.

Slippage determines a range on the price curve that contains the likely price at which the order is filled or closed. So with 1-minute bars and 10 seconds slippage the order is filled from within 1/6 of the estimated price curve inside the bar.