I have built one gravel 25x2800 airstrip. It is not registered with the FAA. Depending on what kind of land you start with, it can be relatively easy, or a massive job. Big boulders are a killer, and require blasting. I was not prepared to blast. Mine was on 22Ac of fairly flat scrub. I also maintain a turf airport. The starting point is the same for gravel or turf, but once it's cleared, and graded, you need to seed, and water of course.
My gravel airstrip is in S NM. I have a road grader, a tractor with several attachments. Clear it with a brush hog first. Use a Harley rake if there's a lot of scrub(I had to remove a lot of low scrub) then grade it with the grader. , then a 3pt tine rake to make mounds of scrub. Burn it off, then use the tine rake to move rocks to the sides of the runway. Grade again from the edges in toward the center to give about a 1.5-2deg crown. Flat grade if it's going to be turf.
It's not complicated work but plan to spend a few weeks on a tractor and grader, and have the attachments needed rather than rent. Blade, box blade, Harley rake, tine/rock rake, brush hog. If you have bigger scrub, you might need a scarifier.
You could hire me to do it, but I'm not cheap.
