Quite a long ways back, I talked about a scale of wilderness travel below the hexcrawl, which I dubbed as "subhexcrawl". I started doing some random tools for generating subhex terrain on the fly, which I'll probably re-do; in fact, my general random sketchbox tools incorporated some of those ideas. But those are for the random terrain approach; I didn't really address the general topic of how to plan or map for the subhexcrawl if you aren't planning on going "full random". But a recent forum post made me think I ought to address that now.
Basic Scale: 120 yards per hex or square.
Time Scale: Same as dungeon exploration, with ten minute exploration turns. You travel one hex or square per turn, up to five hexes/squares per hour with one turn of rest. Unencumbered, unarmored individuals can travel at double speed without actually running, but they can't map at that speed.
Planning: I think the best approach to mapping or planning a subhexcrawl adventure would be to think in terms of landmarks and paths.
A landmark, in this case, is something that can be seen while traveling and that differentiates one area from the next. Reasonably-sized terrain features (individual hills, copse of trees) and settlements of hamlet size or larger count as major landmarks, as does anything that is obviously visible in the surrounding terrain. A single tree, taller than the rest, counts as a major landmark, even when it's in the middle of a grove of trees. A shorter tree with a symbol carved in the trunk is a minor landmark; in other words, it's not visible from a distance, but must be located and approached.
Some terrain features, like ponds, pits, or gullies, and individual man-made structures, are either minor or major landmarks depending on their visibility. A large pond in flatlands is visible from a distance, so it's a major landmark; the same pond in the middle of the woods is a minor landmark. A tall tower on a hill might be visible even over the tops of trees in the woods, so it's a major landmark; the remnants of a tower, or a single hut, is only a major landmark on the plains, but a minor landmark in the woods or nestled between hills.
Major landmarks are for navigation purposes: the players can say "let's head towards that hill", even if there is no road to follow, as long as they can see the hill. Paths are roads, trails, or streams that you can follow; they will connect minor landmarks to each other or to major landmarks, such as settlements. Each hamlet or town should have paths in and out, leading to other hamlets and towns or to landmarks that may or may not be visible; they should twist and turn, perhaps only a little over flatlands, but much more through hills or woods, and each point where the path changes direction has at least the potential for a minor landmark: a cabin, a notable boulder, a burnt tree stump, a signpost, a royal mile-marker, a cairn, or even a fork in the road, with a new path leading to more landmarks.
Process: Start with the homebase settlement, any known nearby settlements, and major terrain features as major landmarks. The local dungeon also counts as a landmark, but whether it's major or minor depends on the above-ground structure or entrance and its visibility from a distance.
Connect the settlements and possibly the dungeon with paths. Give the paths some interesting twists.
Sprinkle some other major landmarks into the area, and perhaps some notable man-made minor landmark structures that are still in frequent use. Connect some of these with paths, depending on which ones are likely to be visited fairly often. Leave a few major landmarks without paths.
At each twist in a path, consider placing a minor landmark. You can use a random roll to decide whether to place a landmark (5+ on 1d6 = landmark.) Or, since streams and roads usually change direction to go around an obstacle, you can assume that there will always be a recognizable terrain feature, like a stone outcropping, at every bend, and only worry about where to place interesting minor landmarks, like the old tree with the name of a forgotten wizard carved into it.
Sprinkle a few other minor landmarks in the area. These are not connected to the paths you've already placed. In mostly clear terrain, the minor landmarks will be small (tiny spring, scorched foundation of a long-forgotten building) and not noticeable from a distance. In hill country or woods, where vision is obstructed, you can place larger landmarks, as long as they aren't visible from a distance. Each of these will have something interesting, possibly leading to backstory, or possibly just providing a resource.
Add some more minor paths leading to/from some of these minor landmarks. These paths will lead somewhere, but not to any of the major paths or major landmarks you've already placed. This is so that a party venturing "off the beaten path" can stumble across either a minor landmark or a trail leading to such a landmark.
... And so on: you can keep extending paths, placing minor landmarks along the paths, or sprinkling other minor landmarks into the hidden nooks of the terrain for as long as you wish.