Things that might help- get a timer (sand, stop watch or one of these ecx.images-amazon.com/images/I/31-l6fTx7HL.SL500_AA300.jpg )
Something visual, so they can observe that time is moving by & when time is finished. Establish a time, maybe special time or quiet time or something & tell your little one that you are both going to spend time doing something on your own. Ask him what he would like to play with during that time (initially it will probably be the timer!) Initially you might like to stay in the same room. This might be a chance for you to read a book or something similar.
Set the timer. If he comes to talk to you *unless it is urgent or an obvious emergency. Just remind him it is quiet time and that you can help/play/talk when quiet time is finished. Turn off distractions.
As you continue to keep the routine you can encourage him to think about it a bit more. Reflect- "remember yesterday you needed a drink during quiet time, shall we get everything ready before hand so you have it with you?" Encourage him to think about what he will need. What he needs for his activity, does he need to go toilet or have a drink available. Prepare together so that you can each enjoy your 5-10 minutes peace. As he gets better at preparing & understands it will be a regular routine that you will stick to you can stretch it longer.
It is key to treat this as a normal, expected part of life. We each need time to ourselves, to rest, reflect & recuperate. So it is not a punishment or a favour that he is doing you. So you present it as a normal, every day, part of life.