Having a full bed dedicated to greens and herbs is one of the most fantastic things I can imagine. Given the proper conditions, lettuces grow quickly, and are ideal ornamental edibles that need little care or space and have few pests (aside from the occasional slug, who rarely touches the arugula or more pungent herbs.)
To set up your own lettuce bed this summer, pick an area of your yard or patio that gets early morning or midday sun, but partial shade when it gets hot later in the day. I navigate the summer growing season by planting both varieties that are slow to bolt (like Red Seas or certain heirloom butter lettuces- check your zoning for what will succeed in your area!) as well as by broadcasting new seeds throughout the growing season. If you’re starting from scratch, try finding a six pack of greens at your local nursery to begin, and plant with room to grow. Once they are established and harvestable (about doubled or tripled in size) begin broadcasting seeds by scattering a few dozen or more around and between the established plants. Water thoroughly, and within a week or two you should start to see new seedlings! I find that the established plants help to shade the seedlings, ensuring a higher percentage of survival, and good practice in succession planting so that when the original plants begin to bolt or get too tough, you will still have a garden full of fresh organic salad greens all summer long.