Wash cool, buttoned up, and don't overload. Woven cotton shirts hold their shape best on a gentle 30–40°C cycle with the buttons done up and the collar flat, in a drum with room to move. Crowding is what sets deep creases and strains the seams; a lighter load comes out far easier to press.
Dry on a hanger, not in the machine. Hang oxfords straight from the wash on a shaped hanger and most of the wrinkles fall out on their own. Brushed flannel keeps its soft nap and deep check if you dry it away from direct heat and don't tumble it hard — heat is what flattens the brushed face and fades the colour.
Iron the oxford damp, refresh the flannel with steam. A crisp oxford collar and cuffs come up best ironed while still slightly damp on a medium-hot steam setting, working from the points inward. Flannel rarely needs a hard press — a pass of the steamer, or a warm iron through a cloth, lifts the nap and keeps it looking like a shirt rather than a bedsheet.
Rotate and spot-treat. Give a shirt a day between wears so the fibres recover, air it rather than washing after every outing, and lift collar and cuff marks with a dab of detergent before they set. Worn in rotation and washed gently, good cotton shirting softens without wearing thin.