Simple Tablesaw Cutoff Sled
Here's a simple sled that's easy to make and will give you very accurate cross cuts.
A slot runner to fit in the miter gauge slot on your tablesaw. I use a piece of aluminum 3/4" x 3/8" x 20".
A piece of plywood or MDF. Most hardware stores sell white plastic coated MDF shelves about 12"x24" for a few dollars.
A fence. I use a piece of aluminum angle.
Make the Sled:
Attach the runner underneath the plywood. Leave about ¼" to the right of the runner to allow the blade to trim the sled perfectly.
Slide the sled along the tablesaw with the runner in the left miter slot to trim off the excess wood on the right. This gives you a perfect line to measure the fence against.
Mount the fence and make a few trial cuts to get the fence at the precise angle.
Rather than making an adjustable sled, you can make one sled dedicated to 90° and another dedicated to 45°. You'll find that once you've got the fence adjusted perfectly it's easier to have a few dedicated sleds rather than re-adjusting the fence each time.