A sawhorse is a great tool to have when using a circular saw, but if you don't have one available, there are still ways to cut wood safely and accurately. Here are a few tips on how to use a circular saw without a sawhorse:
1. Place the piece of wood you want to cut on a stable surface. A table or countertop will work fine. Just make sure that the surface is level and firm so that your circular saw doesn't wobble while in use.
2. Use clamps to secure the piece of wood in place. This will help keep it from moving around while you're cutting, and will also help prevent kickback (when the blade suddenly pops out of the wood).
3. When cutting, always hold the circular saw with two hands. One hand should be on the trigger and the other should be gripping the front handle firmly. This will give you better control over the saw and help reduce fatigue as you work.
4. Make sure that your cuts are straight by following a line that you've drawn on the wood beforehand. If possible, use a guide rail or straight edge to help keep your cuts nice and even.