Plan the location for your court. The playing surface for a doubles-based tennis court is 36-by-78 feet. When you factor in the space needed outside the lines, having 60-by-120 feet is ideal. The area should be level and on firm ground. A north-south orientation is ideal for most play.
Decide on the type of clay court you want. While the red clay of the French Open readily comes to mind when considering clay for a surface, there are other types of clay, including Har-Tru, which was the surface for the U.S. Open from 1975-1977, and synthetic clay.
Part of this decision will be based on your geographic location. Clay requires constant watering, so it does not dry up and crack, so a red clay court is not practical in a desert-type locations.
Consider hiring someone with experience building clay courts. Clay courts are not practical as a do-it-yourself project because the construction of a traditional clay court requires multiple layers underneath the playing surface. For instance, the fast-dry clay of the French Open has five layers: the top layer of crushed red brick, followed by a limestone layer that is about 5-cm thick, a layer of iron ore slag, a layer of crushed stones, then a base layer that has been treated flat. Synthetic clay courts, however, are built on top of a pavement layer.
Plan for any amenities you might want on the court, such as a water fountain, benches and a place to store equipment. Discuss with the contractor whether you want a full-size fence all around the court or only at the back.
Plan your maintenance of the court. After the contractor has built the clay court, you will need to maintain it. The court should be compacted with a roller once a week. After playing on the court, you should water it to maintain the condition of the clay, unless it is synthetic clay. The court will need to be swept and the lines cleared with a special line brush.