You’ll naturally feel more weight on your back foot, however it’s important to keep your bodyweight travelling forward through impact on to your left side. Keeping your weight on the back foot can knock you off balance and cause you to hit the ball fat or thin.
An up slope will have the effect of increasing the loft on your club. To compensate, take a lower lofted club than normal. A lob or sand wedge is probably not the best choice here as you’ll have to have the confidence to hit the ball quite hard all the way to the hole. Cheers!