asparagus in a raised bed

choose what ever height you can afford / manage

Mine are in a bed but I don't build them up high; just 4 planks on the surface to differentiate between path and bed.

Just make sure you dig down into it by 2 spits depth first, to loosen the soil, add manure and make the ridge for them to sit on, and then cover them completely with the rest of the soil.

Keep it watered for a few weeks but not waterlogged and they'll establish quite quickly.

Don't know if I'm preaching to the converted or not, but don't harvest any spears for eating for the first year or two to allow the plant to build up energy reserves and cut down the foliage in autumn when it turns yellow.  it will more than pay you back for years if you can hold yourself back!