League of Legends, like most other online multiplayer games, can be harsh to beginners. Not because the game has a steep learning curve or crappy tutorial system. But because the community can be unforgiving to anyone still learning the ropes. If you want to sharpen your claws, you would have to do it on-the-fly. Like, in the middle of a competitive match.
And depending on how accommodating your teammates are, it could take a lot of time to practice even the most basic things such as last-hitting creeps. For new players who don't really have an abundance of free time, that's a no-go. Thankfully, Riot Games has finally greenlit a sort of sandbox mode where you can freely practice without repercussions: the "Practice Tool."
The Practice Tool, according to the official announcement, is particularly focused on five areas, which includes map familiarity and jungle practice. And yes, last-hitting is included, too. There are a number of commands that will be at your disposal, allowing you to freely control scenarios in the game. For example, if you want to practice an efficient way to feast on jungle monsters, you can use a command that respawns the jungle immediately.
If you have a deep loathing for turrets, you can make them invulnerable and just repeatedly hack away at them until you've had your fill. Hey, everyone has their own way of dealing with frustration. If you want to be more time-sensitive of your actions in a real match, like what you're supposed to be doing at the 5-minute mark, you can fast-forward the game time. And if you don't like what you're seeing, you can easily reset the game. Although not exactly limitless in terms of features, the Practice Tool should be more than enough to get you from beginner to semi-beginner status.
Practice Tool has no definitive availability time-frame yet. The official post only states that "the doors to the Practice Tool training gym will be open soon." In the meantime, you can toil around in unranked matches for practice. The advantage of that is you get to practice hearing insults from everyone. That's something the Practice Tool will unlikely cover.
Source: League of Legends