Can I share the booking page link directly on Instagram?

Yes. The booking form lives at your own address followed by /book, and the Book a table button on your ordering page goes there too. The page itself is kept out of search results on purpose, so a direct link is the way to send people. It only works while at least one table is switched on and your plan includes dine in. The Tables, tabs and the kitchen screen tab in the docs explains where guests find the form.