Prepare and Connect New Supply Line to Faucet

What happens here

Obtain a new braided flexible supply line of the correct length and connection types (e.g., 1/2" FIP for the faucet, 3/8" compression for the angle stop). Carefully thread the faucet-end connection (typically the larger 1/2" FIP side) onto the corresponding threaded pipe extending from the underside of the faucet. Hand-tighten this connection as much as possible to ensure it's properly seated without cross-threading.

Goal: Take the new braided flexible supply line and hand-tighten its faucet connection end to the underside of the faucet.