Yes if you are deviating from the industry recognised standard operating procedure for this element of your operation, then you should risk assess and document this.

It depends on the angle of the slope and other factors too, if it is only a gradual slope with good adhesion for example, this will reduce the risk factor considerably.

Just to add my background Louis, I am a qualified forklift truck instructor since 1996.

Standard procedure is that loaded forks should face uphill, and empty forks should face downhill, but there are exceptions to this rule, one example is when loading or unloading vehicles usong a ramp, where there is insufficient space to turn the forklift truck within the vehicle.