Open your cheat box and enter the following:
moveobjects on
boolprop snapobjectstogrid false
boolprop allow45degreeangleofrotation true
Now, while you are in buy mode you'll be able to move your sims as needed, but you'll need a fair degree of patience, because sometimes sims have a habit of jumping into weird angles when you get them too close together
And if all else fails (i.e. sims still insist on making symbiotic relationships with the other sim upon being moved closer to them), and you happen to have OFB installed, you can use the cheats Joy mentioned along with placing one of your sims on an invisible Magisplay Tray. The invisible recolor can be found
here, but you must be sure you have Numenor's CEP properly installed in order for it to show up right.
If you don't have OFB, there's always the OMSP (One More Slot Package) series and variations on
MTS and around other sites in the community. Personally, I use the "Basic Base Game OMSP" version of
SilentLucidity's collection when I want a sim flat on the ground... and it may seem like a lot is there (and believe me it is), but the collection only files helps to cut down on that Buy Mode clutter.
Putting your sims on either will prevent them from "snapping" into the open slots on a sim, and you can move the slot package while the sim is on it, so it's very helpful at times. But be forewarned,
do NOT save and exit your lots while a sim is placed on any of those two... otherwise, that lot will become corrupted and unusable. I've made that mistake plenty of times in the past and wondered what went wrong when I couldn't load my lots even with debug mode enabled.
Be very sure that all sims have their feet firmly on the ground before saving.
