There are many variations of planks that help increase core body strength, here are some you can start with:
Side planks help you work out a minor core muscle called the quadratus lumborum. Researchers have found that exercises similar to the side plank that work on the endurance of your lower back can substantially reduce the risk of back pains. Because the side plank is tougher than the normal plank, start by trying to hold a side plank for 3 sets of 10 seconds and work your way up to 1 minute to achieve maximum results.
Three-point planks improve on the regular plank by eliminating one of the contact points involved in a normal plank. Hold your body in neutral position and raise one leg off the ground and hold it for 5-10 seconds and then alternate while making sure your body doesn't lean sideways.