Measure the starting point or high point's height and calculate how long your ramp needs to be. Hammer stakes on the sides the full length of the ramp, making sure that the stakes that are across from one another are at least 36 inches apart for the width of the ramp. Run string between the stakes to make an outline of the ramp.
Pile fill dirt in between the outline with a shovel. Slope the dirt away from your high point down to make a gentle slope away from it. Measure the height of the slope often to make sure it does not exceed 1 foot tall for every 12 feet long. Dampen fill dirt with water while piling to help settle the fill dirt, let it dry, then tamp it with a tamper. Repeat until desired height is achieved.
Let the ramp settle for a few days, then tamp with a tamper and adjust as needed with fill dirt. Let it settle if adjustments were needed. Tamp the surface with a tamper.
Lay a 1- to 2-inch layer of fine gravel on top of the dirt ramp. Tamp the surface down with a tamper. Test the ramp before using with a wheelchair.