For me the act of successfully foraging is simply subsisting on what you find, with the "Base" being what's needed (Food and Water) to survive one day.
That, in itself, can be very subjective.. Let's say you find a source of drinkable water, is it a puddle or a stream? Is it the remains of recently slain creature? Is that creature a elephant or a mouse? Do you find rough barely edible plant matter (grass) or an Apple tree? All could enable you to survive, but some might allow survival for more than one day or serve to feed more than one person but ONLY for one day. The point here, is that the magnitude of the possible success is generally a random factor, which is heavily influenced by the availability of certain factors, ALL of which are under the control of the GM. The skill check result is reflective upon that pre-set availability. Therefore, if the GM knows that there is little to no food/water in an area then the roll will be at a severe penalty or the results of an otherwise successful roll will simply net less.
Now, *how* and "why" the character forages must also be figured into the chance of success. Foraging by it's very nature does requires movement... and is essential for repetitive successful attempts. The direction is not so important, but the speed of travel is.. so the faster the person travels the less effective they are... or they? Bear in mind that unless they are either completely sense-blind or rendered thoughtless of action, a player should be allowed to instinctively call upon the knowledge that their character has of their surroundings. Any amount of reasonable knowledge will enable a character to identify common fruit, and distinctive plants whilst moving better than someone who simply wanders around aimlessly in a set specific area with no idea of what can be found or, indeed, what can be done with what is found whilst doing so.
Thus travelling at a walking speed whilst knowledgeable about what could possibly be found in an area should allow foraging for survival at no penalty to the overall distance travelled for the day especially if the characters prime focus is travel. Better rolls simply net more stuff or better stuff.
Foraging can also discover, un-looked for boons, like herbs appropriate for the terrain type. Whether the character knows what it is another matter.
Other skills also reflect upon the utility of the Foraging attempt, Flora, Fauna & Herb lores. The Survival skill may also modify the difficulty set by the GM.
Basically, If that requires 4 hours of nothing but foraging.. that is a basic roll, and that's what's achieved. However, other factors need to be introduced in to the success (or failure) of the attempt.