I don't recall exactly where I heard this, but I've used it and it works.

It works for any major objective such as Rift Herald, Dragon, or Baron, but we are specifically going to talk about Baron because high Silver/Low Gold teams often struggle with closing out games especially if the enemy team has decent wave clear and so you need Baron enhanced minions to help with sieging.

Push the enemy team out of the side of the jungle where the Baron resides. Then place a Control Ward in the Baron pit. One in the bush beside Red and one in the bush by Raptors and then sweep the area of enemy wards with an Oracle Lens.

It is now very dark for the enemy team on that side of the map. They either have to come and check on the baron or risk giving it away for free. If one or more enemy champions come to check, kill them and then you should have an uncontested Baron, especially if one of your picks was the enemy jungler.

And yeah, you need your team to understand what you want and help with warding and sweeping the enemy jungle, but it is sometimes possible to direct them to accomplish this.

I've noticed that if my team is already competent with warding and laning (and they probably are if you are in the lead) then they usually understand the concept and can help you laying the foundation for a successful Baron take.

E.g. You are constantly blooding the enemy any time you run into them and send the scurrying back to their base. Okay, you have a lead.

In chat type "ward and sweep enemy jungle and look for pick. Then Baron."

That is usually sufficient to get the message across.