Cut the dough in two and work with half at a time, leaving the rest in the refrigerator.
Lightly dust your work surface with flour and roll dough out to roughly 18"x9" and use a sharp knife to cut into triangles (for classic croissants) or rectangles (for pains au chocolat). For medium-sized croissants, cut each sheet of dough into thirds (6" x 9" rectangles). Then cut each rectangle diagonally, corner-to-corner, to create 6 triangles. Repeat with the other half of the dough for 12 croissants total.
Cut a small slit at the base of each triangle and roll your croissant, pushing outward gently with your palms while rolling to elongate the croissant.
Place on a lined baking tray with the point or seam of the croissant on the bottom.
Optionally, you can whisk together 1 tablespoon agave or maple syrup with 2 tablespoons plant milk to make a vegan egg wash substitute. Lightly brush the croissants with this mixture to help them achieve a glossy finish. (Reserve the extra; you will brush them one more time before baking.)
Allow croissants to rise at room temperature for 1-2 hours, until at least doubled in size.