Make them large enough to leave in place for several years. Finish filling the hole with soil mix. The crown should be at or just below the soil line. No more than an inch of soil over the crown. The crown is the point of the plant where the roots and leaves meet.
Daylilies do fine in raised beds as long as there is good drainage.
Most like regular and frequent water during the heat of summer, especially when in bloom. They will benefit from an organic mulch. Use it an inch or two deep, keeping materials like grass clippings several inches from the base of the plant. It is advisable to 'deadhead ' the plants during the flowering season. This keeps them neat looking and prevents unwanted pods forming.