Hello William, These gats are very cheaply available - new or used. Might not be worth your while trying to make one.
Here is one made from an old pallet. https://www.hometalk.com/36744284/diy-baby-gate
Go to face book market place / Craig's list, ask if anyone has one they are getting rid of, you may get it for free. These things end up on the trash pile - more expensive to build one.