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If the "about" 4' measurement allowed it to be split and still retain 24" for each piece this is how I would handle it.
I would rip the 3' width down to 30". Then put it on the crosscut sled and cut the 48" length in two to get the 30" X 24" pieces. 30" would be about the maximum crosscut for my sled, but a bigger one could be made rather cheaply if needed.
First you have to make sure one side is straight. If it was solid wood I would run it through a jointer. However in your case I would clamp a piece of known straight wood to the board near an edge to form a straight side and either use that against the fence or the table edge cut the other side straight and parallel.
Then I would put that side against the rail in a crosscut sled and cut that side exactly 90 degrees to the two parallel sides. Then all that is left is to cut the opposite side either in the sled or against the fence.
Everyone forgets step one. Make sure the first side is straight, if you put a crooked board against a fence you can end up with a crooked cut. To me the jointer is the second most important tool in the shop.
I have run MDF through the jointer to get the first side straight - no problem. Use a very shallow cut (and multiple passes if necessary), and expect a very fine dust (like sanding - you may want a face mask) rather than shavings.