I, actually, prefer that beginning barefoot runners start on rough, rocky, uncomfortable terrain
But not necessarily running, and certainly not long, or fast running, right from the start… Start with standing, and feeling the terrain with your bare soles. Then walking, focusing on walking gently. Then, much later, running barefoot. After you master running barefoot on rocky, pointy trails, everything else will be tasty, sweet, delicious desert!
If a fraction of mile is all you can do (especially if not comfortably), then it’s time to focus on technique, rather than distance.
Stand first, then walk, and much later, run barefoot on the new terrain.
Start with standing, and practice letting your feet relax, and mold into and over and around the sharp pebbles, etc… Be sure to relax your legs, and bend your knees (while standing), torso vertical, hips slightly forward (at least they will probably feel more forward than you are used), and keeping your soles entirely grounded.
Do not PUSH your soles into the ground! Let your feet mold gently to the terrain.
When you can stand comfortably, relaxed, on this surface (might be hours, might be days, might be weeks), then you can start to take one step, at a time.
Slowly lift one foot at at time and practice standing on one foot, same as above, bent knees, vertical torso, hips slightly forward, relax, and this time, let just one foot mold to the surface with the other foot lifted off the surface – remember, bent knees.
Practice, practice, practice.
With each step, re-evaluate and again practice letting the entire sole ground, to distribute your weight over many points,(instead of a few as when tensed). Relax, relax, relax… knees bent, torso vertical, hips slightly forward (no slouching).
When you can do a few steps (in place) this way, then you can start walking short bits. But do not push with your foot, just gently and slightly move your hips forward while lifting one foot. Then set that foot down, directly under (not out in front) of your body
Again, focus on letting the entire sole spread out over the surface, bent knees, vertical torso, hips slightly forward, and relax, relax, relax.
When you can walk a bit of distance (half-mile to a mile) comfortably, then you can try running inplace, with fast cadence, bent knees, vertical torso, and relax, relax, relax…
This time, focus on keeping your head at a constant level (or nearly constant level), if you feel your head bouncing, or when looking of at the horizon, you see the horizon bouncing, then focus on lifting your feet, rather than trying to push your body up with your feet. If your knees are bent enough, and you lift your feet quickly enough, your hips, body, and head should be able to nearly float in one place while you lift your feet quickly.
When you get the feel of that, then, without changing your cadence, or posture, simply push your hips, very gently, forward, slightly more. Don’t panic, just keep lifting your feet quickly, think of peddling a bicycle in low gear.
Anytime you start feeling any jarring, jolting, pounding, or jogging sensation in your body or on your soles, go back to the previous stage (running in place, walking, or standing).
Anytime you are running, and feel discomfort, is a perfect time to reevaluate running technique. As I said at the start, “Once you get rocky, pointy trails down, everything else will be desert!”
Which is exactly the reason barefoot runners should NOT try to avoid uncomfortable terrains.