My overland exploration procedures typically allow for three possible activities. The first is resting, the second is travel, and the third is searching a hex. This article is about the third procedure, searching hexes, and in particular, how to execute step #7, "Referee determines whether the PCs find anything". I'm going to discuss this step from two angles - firstly, placing content in hexes and secondly, the PCs conducting their search.
As a reminder, I use hexes with a 5 km radius from centre to edge (a 10 km incircle diameter or "10 km hex" for short). A hex this size contains 86.6 square kilometres of area. Here's a calculator that will tell you the dimensions of hexagons of various sizes (metric) if you want a different size.
The Placement of Content in Hexes
My solution here is very simple. Hexagons divide into six equilateral triangles.In my hexes, each triangle covers an area of about 12.5 square kilometres, with a maximum distance of 5 km from base camp (assumed to be in the centre of the hex).
I number the triangles from 1 to 6, and roll 1d6 to determine which subsection any particular piece of content is in. ktrey over at d4 Caltrops has a tessellation system that breaks hexes up into 12 lozenges of equal area if you would prefer that level of granularity, but in all honesty my hexes rarely have more than two items in them at a time to start (not counting wandering monsters) so I don't have much need for that level of granularity.
I also assign each object a Concealment Score that interacts with my group perception rules. When in doubt, I randomly roll a Concealment Score of 1d6+3, knowing that anything with a Concealment Score equal to or lower than the # of PCs is going to be automatically spotted when they enter the hex. I try to make something immediately obvious in at least a third of all hexes, sometimes as much as a half, depending on how aggressive and interested they are in searching hexes.
In step #1 of my search procedure, PCs break up into search parties and each search party chooses a subsection of the hex to search. The most common choice in actual practice is that they all stick together and make a random roll of which subsection they're going to search, but they have the option to split up if they're in a rush or feel confident.
PCs searching a hex counts as an active search, so they roll 1d6 and add the # of PCs in the search party, and if it equals or exceeds the Concealment Score of the content, they find it.
A single iteration of a search takes one watch to complete (typically 6 hours), including time spent returning to base camp. Multiple search parties searching different subsections do their searches simultaneously.
This means that if the PCs stick together and search a hex, they will clear it in one full day (6 watches) of searching (without rest), or 2/3rds of a hex if they do. My experience is that they tend to work to the 2/3rds level by spending a day searching before moving on.
I'm not sure of how realistic this is (probably not very), but it strikes a good balance between giving them a change to discover a lot of content and leaving a level of uncertainty about whether they've truly found everything.
Lazybones / No Prep Method
If you're in a rush and having had any time to prep, you can just roll 4d6, preferably of different colours, when the PCs search a hex. The first is the subsection the content is in, the second is the subsection they search, the third is the Concealment Score and the fourth is their active search roll.
If the first and second die don't match, the PCs don't find the content because they're in the wrong spot. If the third die's result is higher than the fourth, the content stays hidden.
I usually do d6+3 for an actually randomly generated Concealement Score, and the fourth d6 will be +# of PCs since it's an active search, but you only have to get to these calculations if the first and second die match.
Once you've rolled the subsection the content is in, I suggest mostly keeping it consistent across further searches because a) it means fewer die rolls and b) it makes things less frustrating for the players because they can whittle down the location by progressively searching all of the subsections.
The sole exception I can think of where it becomes more fun is if the content is moving (e.g. it's a fugitive trying to hide from them by running around the hex), and this will incentivise the PCs to break up into smaller search parties to search more subsections simultaneously. In this case, you should still only roll the first d6 once per watch of searching.
I find these methods allow me to quickly establish whether the PCs have found anything when they search. You have one roll for stocking, and one or two rolls to resolve searching. The level of risk and difficulty of this system can be adjusted using three factors - the granularity of subsections (more likely to miss things), the length of a watch (more resources consumed, esp. time), and the Concealment Scores of content (more difficult to ensure you've cleared a hex). I hope this helps you stock hexes more easily.