Get the cardboard and measure the base 45 cm and height 30 cm. Cut out the cardboard and make the inner square. Attach the remote control car to the backboard.
Cut a PET bottle in half. Cut it again. Now you should have a nice rim. Tape the rim to the backboard.
Make a rectangular box and stick the character (Shaq) on it. Attach the bits (vibration motor) to the character.
Make a square, doesn't matter how big because that square is the 'bouncing zone.'