I usually pull out some saw horses and a peace of plywood to use my mitre saw. You can actually see that arrangement in the background of one of my pics below.
That works OK but this is definitely an upgrade. This cart is made from a single piece of plywood and four 2×4’s (and a couple of scrap peaces as well). I love having the Home Depot folks use their panel saw to save me some time. The only problem is their blades are often dull and result in lots of tear out. The casters are from Harbor Freight.
This is really a blended item. It allows me to use the mitre saw, provides some work space, has shelves, and a place to store my clamps. And my dad got to help a little, he is the guy that really started it all for me.