What should be removed before creating an arch in the eyebrow?

Before creating an arch in the eyebrow, it's essential to remove makeup to ensure a clean and even surface for shaping. Makeup can interfere with the precision needed for eyebrow grooming techniques, such as waxing, threading, or tweezing. By clearing away any makeup, the esthetician can better see the natural line of the eyebrow and assess its shape, which is crucial for achieving a balanced and flattering arch.

In the context of the other options, while it is important to consider products like moisturizer, foundation, and pencil liner, makeup removal is prioritized as it directly impacts visibility and precision during the shaping process. Foundation and pencil liner typically fall under the broader category of makeup, and while moisturizer can affect how products adhere, it does not obstruct visibility in the same way. Therefore, removing makeup is the most critical step to ensure accurate eyebrow shaping.