A sandbox game mode without the risk of lag

This is most likely a silly post that won't accomplish anything; but, I figured there was no harm in bringing it up.

I really wish there was some sort of sandbox game mode that I could play without the risk of lag. Unfortunately, due to my currently situation at home, I'm very limited to when I can play this game without lag (basically, I can only play if no one else in my house in using the internet). Because of this, I would rather spend that rare time playing real games rather than diddling around. I would love to have a freeform, sandbox mode where I could play without the risk of lag, and get to practice champions and techniques.

I actually got this idea because someone a while ago had a thread going about offering a sandbox mode where players could change variables, such as timers, in order to practice strategies. For example, if you're new to the game, you might struggle flashing over walls. If there was a sandbox mode, you could play in that mode, remove cooldowns, and practice flashing over walls endlessly, without needing to wait three minutes.

Maybe you need to practice certain champion combos? Some champions can make the most amazing plays, but only if you time every move correctly...

I would love to have access to a game mode like this, if such a thing was possible...