THere are untold number of engines stored "on the ground" at this monent. The engine has no idea as to whether is is stored on the ground, on a shelf or in a car. As long as you don't drop it onto the ground, the oil pan will support the weight or the engine. I have a spare engine sitting on the floor of my workshop garage at this moment (been there since I pulled it for the '78 that is in my car at the moment - someday I'll rebuild and reinstall this one as it has the road draft port where my early (CA specific) EGR system plumbs into). I do not have the garage space to keep the engine stored on the engine stand.
The only downside to an engine on the ground is that it can roll over if bumped - I would suggest, if you have the room, to store it in a corner leaned up against the wall. If you have a junk tire, set the engine into the tire to support it or make up a wood crate out of 2x6 to support the oil pan sump and to stabilize the engine if you can't lean the engine against something.
If you have not pulled the engine yet and it is in running condition, you might want to fog it w/ a light oil to prevent corrosion inside the bores or pull the plugs and pour about 1 table spoon of light wt oil into the bores and turn the engine over to spread the oil - don't forget to reinstall the plugs afterwards. Personally I have never bothered to lube an engine prior to storage - depends a lot on where you live (and how humid it is).