The ones I plant for seeds I space out by eye in curved rows just standing in one place. For the actual crops, I stand in one place, spin, and plant in a spiral. I allow for some losses, also don't care if planting is initially 'healthy' - they'll either grow when the others mature or they'll go in the loss column.

Usually I have one or more remote farms at stone circles. They are flat enough to just cultivate without leveling and easy to just throw up some pole fence between the stones to stop greyling intrusion. Later on, if I start farming at night, I'll upgrade the pole fence to a stake wall fence.

Harvesting, I turn on walk mode (default 'C' key), hold 'E' down, and just walk along moving my cursor on the mature plants.