My asparagus crowns arrived today from Kings Seeds, only a quid each and they came with excellent planting and aftercare instructions. In previously dug and composted ground I took out a trench 30cm deep and wide, ridging up the middle of the bottom of the trench 5cm, spacing the crowns 50cm apart on the ridge with the roots spread out:
Then covered up the roots and firmed in:
I'll fill up the trench as the plants grow. It'll be a couple of years before I can cut a decent amount of spears but it should be worth the wait.