Wash at 30°C delicate cycle. Maximum 40°. Minimum spin.
Linen being a material that dries quickly, hanging it out in the open air is ideal, and the wind smoothes it out naturally!
You can also dry it once in the dryer at low temperature: this will make your linen pieces even softer! (slightly damp "iron-ready" mode at the end of the cycle)
Never iron your linen garment dry: iron upside down, hot iron on damp cloth or with a lot of steam.
Your linen pieces will get softer over time, wash after wash.