How exactly do I shoot a springer from a bench?

Do not clamp it. Rest the forestock on a soft sandbag at the gun's natural balance point with the bag well forward of the trigger guard.

Do not pull the gun hard into your shoulder; let it sit in light contact. Trigger hand grips the pistol grip with a relaxed, repeatable pressure. Cheek weld is consistent every time. Allow the gun to recoil freely off the bag. After the shot, hold the sight picture for a full second of follow-through. Same hold every shot.