For several easy core work-out demonstrations, check the website below.  You will find mini-videos as well as written instructions.  The general website offers a large library of exercises for multiple levels and multiple areas of the body.  Once at the website, place your cursor in the instructions for an exercise.  This causes the video above the instructions to play, providing a demonstration of the exercise.

https://www.acefitness.org/acefit/fitness_programs_core_workout.aspx?workoutid=5