Don't make the mistake of waiting for spring to sow the seeds. By then the plants should be several months old, not just starting out.
It took three things to make this display happen. Two were of the nature of inspiration from gardeners of the past. If you love poppies be sure to read, and read again and again, Celia Thaxter's An Island Garden.(1894, Houghton Mifflin, available in an excellent paperback reissue of 1988).
Another old book provided another: J. Horace McFarland's My Growing Garden (1915, Macmillan). Color plate xviii shows an eighty foot border planted to mixed Shirley poppies with the caption "An ounce of Shirley poppy seed... sowed along an eighty-foot border... in mid-June came days of poppy glory." Here's a scan of that plate: