In the run-up to Thanksgiving, learning to make pie is a worthwhile skill. Kate McDermott, who wrote “Art of the Pie” four years ago and who has a new book, “Pie Camp,” will lead a series of three virtual classes in pie-making at the 92nd Street Y. The first one covers making dough. Next, the subject will be chess pie, a simple filling (and if you master chess pie you’re on your way to pecan for Thanksgiving). The final session covers fruit pies, notably pear, with a lattice top.