Your time already has a price. Publish it.
People ask for an hour of your attention in DMs, and the answer is a week of scheduling. Publish the hours you are open and let someone ask for one without a single message.
How a slot gets booked
You set the terms; the calendar enforces them.
Choose the windows you are open and who can see them. Plenty of people open a few hours a month for anyone who asks.
Every booking starts as a request you accept or decline, so your week only holds the meetings you agreed to.
Google Calendar sync works both ways: an hour blocked anywhere else disappears from your public availability before anyone can take it.
They booked from your profile, so they have already read what you do and what you have written — the hour starts at the real question instead of the introductions.
Open two hours next week
You can change the windows and the rules at any point.