What base/rock/gravel for run-in/hay barn building?

Kinda quickly I need help with recs for shed---40' x 50' ; 31 feet being storage and 19' run in. we're being told 21 AA on top with "sand" under--base needs building up-
is this right or do I need to cover the 21aa (DRIVEWAY GRAVEL/Road bese its described as)

Do I need geotex if puttung this in?

Is stall/landscape grid OVER it ,then crushed limestone brushed in grid--a good covering or will cleaning out with tractor going to pull it up???

Getting cold feet as dozer is out there now stripping topsoil....tia klr

road base (here that's 3/4"-minus) is a good base for a building but not so much as the finish for a run-in, because there can be large sharp fragments. I'd put something on top that is all smaller (in southern california, decomposed granite, up here, probably "red sand" which is a rounded 3/8"-minus lava rock). Alternately, you could line the floor of the run-in with rubber mats. The right materials are very much a function of what you have available locally at the right price.

If your run-in is 3 sided, you may want to ask them to grade it with a tiny slope so that any water or moisture goes out the opening, and won't puddle, or worse, run into your storage shed. You probably don't want it to end up that the finish grade of your run-in is higher than the storage floor.

The most important part here seems to be getting it up above the grade so water doesn't pool on it. If water doesn't pool, the ground seems to keep its integrity without any geotextile.

I have a south facing run-in/barn with a 3+ foot overhang that keeps all but a wind-driven rain out. It had 1-1 1/2" packed gravel covered by 4-5" of stone dust. The dust was graded to allow outward drainage (maybe 1" of slope over 12 feet) then watered and rolled with a standard lawn roller. It hardened to a concrete-like firmness and is covered with rubber mats. It withstands New England frosts and being hosed out (mats rolled back).