Keeping pasta warm for a long time is a challenge for even the most experienced cooks and caterers. Pasta becomes chewy and dry when kept warm without liquid. Inversely, it can become too soggy and soft when heated in water. A small amount of liquid and vegetable oil are the keys to warming plain pasta for a buffet or potluck. Whenever possible, warm the pasta in sauce to keep it hydrated without overcooking.
Prepare the pasta according to manufacturer's directions. Remove it from the heat and drain as soon as it becomes al dente -- fully cooked but not overly softened.
Place the pasta in the slow cooker with 2 tablespoons olive oil and 2-4 tablespoons water. Toss thoroughly to coat.
Set the slow cooker on low heat. Replenish the water every 30 minutes. Every hour, check for texture and replace with freshly cooked pasta as necessary.