Maybe you saw the other post. I want to put a concretes floor. It doesn't have to be "perfect" just mostly level.

It is ~35'x24' inside so a 4" slab is ~10-11 cubic yards.

Tell me where the plan is BS and destined to fail:
1) Level out the floor.
2) Frame out the garage doors, inside the frame so that the door will shut. The inside walls would be 90% of the frame
3) Pour a 4" slab, once done the slab will push up the sides of the inside walls ~3-4" inside the garage. (removing the garage in the future will be difficult)
...........4a) we feel like the slab above ground level will help keep any rain water out. Also know is may create a trip hazard.
4) Pour a 1ft wide slab beneath each of the garage door, and at the front door.

Any huge problems with that plan?

Ideally we would pour a slab that is ~2ft too long and wide, then set the garage on it. That seems like a much harder plan. If there are no MAJOR issues with the first plan we will go that way.

How hard would it be to jack it up ~4", put cinder block under the perimeter then frame around the outside of the building. Pour concrete to ~1/4" up the sides of the bottom of the wall.

Writing the post above down helps me think thru the process. May take a little more concrete, but would work better.

You could do it either way but sitting the building and n top of a slab would be best. You’ll need some help to pick the building up. Tractor with a loader could pick it up high enough to block under. Or you could pour a slab close to the building and slide it onto the new slab.

3 inches of gravel. Cheaper and easier to.

Jack it up, run boards on blocks across each corner to give working room. Then frame out the floor, pour concrete and set it back down. It’ll give you a better “foundation transition” for a lack of a better term. Do it right the first time or you’ll always regret it.

Make sure the metal is fasted good between the "posts" to the bottom runner. If you plan on doing it yourself and have never worked concrete, find a buddy who has. It not near as easy as they make it look. You can make a float to work it but you should be able to rent everything locally. I'd dig it out to make it 4 inches to the top of the ground runner. Make your door ramps a lot wider than 1 ft.

The guy who is doing my build has done internal concrete pours under garages and pole-barns many times. Its a standard thing for a lot of folks. A mini-ex can drive right in and dig it out. Then they lay the wire if needed and back the mixer right up to the doors. Depending on your weight load and use requirements you may not even need rebar. Its still going to cost at least $5-$10k pending.

Also, figure out if you have plumbing somewhere under that stuff. If not, then congratulations, your decision tree got easier.

Are you going to put plumbing under the slab?? That needs to be done first if you want it done that way.

Great minds!!

Dig it out , even under the frame that's on the ground . As you dig back under the frame you can use bricks to support at each brace and corners as needed. Pour back to level it is now , letting the concrete run under the frame and leaving the supports in. Pour your apron wider than 1' , 3-4 and run it all the way across with a little fall in it. Might need gutters and cut a swell around it to manage water. Almost forgot, anchor the lower frame to the concrete .

Slab that size will need at least one joint sawn in it.

PUT a Moisture Barrier under the concrete.

Yep, good idee.

Jack it up, car jack, bottle jack, FEL, put it on bricks, blocks, frame and pour concrete(if you haven’t played with 10-11 yds, pay the man) concrete waits for nobody. Even if fiber mesh put in wire. I wouldn’t worry about plumbing can always do later just put plumbing on top of concrete and build floor above it for bathroom, shower etc

It would make life mighty easy to plan the bath and stub in drains when pouring .

I'm with everyone who has or will say to either jack it up, pour, then lower, or pour beside and slide the shed over. Either way, anchor to the slab once done.

For me personally, I like to do things once and never have to worry about it again. I have lived in too many half-ass built houses where someone saved a dollar and cost me $500 10 years later because of that to do things any other way. When I am dead, lots of things might be said about me, but building a half-ass house or shed will never be a true statement about me.

I figure that short of a tornado or fire, the cabin we live in now will be here in 100 years.