Hi hope you have a strong back..you should dig down at least 4 inches..remove all earth etc.
Best to messure width of driveway and put strips of wood either side to set distance from one side to the other..4x2 inches of any old timber will do.
The base for the driveway needs to filled with hardcore..old boken bricks etc.all bedded down and then use hardcore a mixture of sand+cement and ballast.
Using a piece of wood that is the width of the driveway and running on the two 4x2 strips of wood you work from the top of the drive to the bottom to keep it all flat and true.
Once that has set 4 days max..then tar over the top.
How easy is that..