Beefy T-Tracks are an option for work holding or just holding in general. To install them you can either create a 1" groove deep enough into your waste board to allow them to sit below the top of the surface or cut your MDF into strips to fit between them. 

These T-Tracks are a larger (thicker) than those available on Amazon or at your local supplier, which increases the strength of them and allowing for the seldom whoopsie. Being that their made of Aluminium, if 4' is too long for you, it is quite possible to cut them on your miter saw using a woodworking blade without any issue.