For medium-sized potatoes, I cut them in half. Then lay each half flat side down and cut them in half lengthwise. cut across the quarters to create pieces that are roughly 1.5″ x 1.5″ x .5″ thick.
Add the potatoes and carrots to a baking sheet along with the garlic, salt, pepper, herbs, and olive oil. Line the baking sheet with parchment for easy cleanup.