Ok, so your specific question has for the most part been answered. (It's doable but generally inadvisable).

I'd just like to add that rather than soloing/duoing baron, having your whole team sneaking baron can be extremely effective in lower elos – specifically when your team is losing and the opposing team has control of dragon. Generally if you have the timer on dragon but the enemy team has control/will flat out win in a fight, you can rush baron down while the enemy team goes and picks up their "free" dragon. As you rise in rank this will probably become less effective, but in Bronze/Silver I've found that teams focusing on early dragon control almost never even have baron warded.

Mind you, messing this up can be catastrophic. But I've turned many "sure losses" into victories by convincing teammates who have all but given up to just try this one last play.

(Also, sorry if this should be a comment. I don't have enough points to make a comment)

Ok, so your specific question has for the most part been answered. (It's doable but generally inadvisable).

I'd just like to add that rather than soloing/duoing baron, having your whole team sneak baron can be extremely effective in lower elos – specifically when your team is losing and the opposing team has control of dragon. Generally if you have the timer on dragon but the enemy team has control/will flat out win in a fight, you can rush baron down once the enemy team heads toward their "free" dragon. In Bronze/Silver I've found that teams focusing on early dragon control almost never even have baron warded.

Mind you, messing this up can be catastrophic. This is more of a hail mary play than a good general strategy. But I've turned many "sure losses" into victories by convincing teammates who have all but given up to just try this one last play.