When building a flower bed there are a number of things to consider. You want to be sure first and foremost, that you are setting up your flower bed in a place where flowers will be likely to grow. This means not only making sure that the area you are building your flower bed in gets sufficient light, but that the soil ph is the correct kind to support the growth of flowers. Once you have established that your plot of land can support the growing of flowers, you can begin building your flower bed.
Generally speaking, the tallest plants should be placed at the very rear of the bed. Ideally the back of bed should be against a fence or garden wall to best support these tall plants and create a nice visual effect. Flowers that require the most pruning, watering and other care should be placed closer to the front of the bed so that you can access them easily without trampling the other plants.
Make sure that you level the soil so that everything in the flowerbed is even, and you have nice, loose soil to work with.
Outline the plot of land that you will be planting in and demarcate where each of the different plants will go by placing household flower to make different spots.
Spray the soil with a non-selective herbicide and allow it to set in for about 2-3 days. This will help the seeds germinate and make sure that no weeds linger to choke your flowers.
Layer the area of your flower bed with compost and other soil amendments designed to help enrich the soil making it easier for you to plant.
Line the perimeter of the flower bed with stones. These should be medium-to-large sized stones, which can help demarcate the flower bed from the rest of the lawn and can also help to contain the soil from spreading onto the lawn.