Preheat a grill to 500 degrees. In a small bowl, mix together the marinara and ginger; set aside. Place the eggplant slices on a baking sheet; brush generously on both sides with oil. Season with garam masala, salt and pepper. Transfer the eggplant slices to the grill; cover and cook, turning occasionally with tongs, until tender and charred in spots, about 5 minutes. Return the eggplant to the baking sheet.
Lower the heat on one side of the grill to low. Oil the grate on that side of the grill. Move the shaped dough to the grill. Lower the edge of the dough onto the oiled grill, draping the dough perpendicular to the grade. For 9-inch pizzas, grill 2 crusts at a time. For 3- to 4-inch pizzas, grill 8 crusts at a time.
Cover the grill and cook until the crusts begin to bubble and brown, about 3 minutes. Loosen the crusts with a metal spatula; cover and cook for 1 minute more. Flip the crusts over; cook until beginning to brown on the bottom, about 2 minutes.
Working in batches, invert the crusts flat side down onto a baking sheet. Spread with the marinara. Divide the spinach, eggplant (chopped for small pizzas) and feta among the crusts. Cover and cook until the cheese is golden and beginning to melt, 2 to 3 minutes.
Try our Best-Ever Pizza Dough