Croissants can be frozen at the end of step 3. Freeze, uncovered, until hard, about 2 hours; transfer to a ziplock plastic bag. Thaw overnight on baking sheets, covered tightly with plastic wrap, in the refrigerator. Proceed with step 4.
Croissants bake most evenly on the middle oven rack. If your oven is large enough to accommodate 2 pans side by side, both batches may be baked at once.