1) Insert a 'New Page' gives me a page with the 'cell' template that is visible in the Page Panel. Dragging a photo to this page places the photo in a cell.
2) Insert (of have) a 'Blank Page' without a cell, then dragging a photo onto the page shows me the photo filling the page with cell handles to allow resize of the cell. But I cannot drag a second photo to the page unless the page template is changed to accommodate multiple photos, or a Right-click [Add Cell > Photo] creates another cell.
Thanks Robert. I had that experience too. In other programs all the photos one wants on a spread can be selected and dragged in and the necessary cells are automatically created.
It seems so cumbersome in LR that I gave up and resorted to Fundy. I had liked the idea of staying in LR to make a book but it is just too labor intensive. Oh well. Hopefully in future it will be enhanced.
We have included this new feature in LR Classic 8.4 release. Please update to 8.4 and try out this new feature where dragging a photo will create a cell automatically.