.... and you really need special tools.
If you're going to make just one frame, forget it. Have it made.
But if you expect to make a few, here's what you need:
A very good mitre saw. Expect to pay upwards of $100 for one. A $15 handyman special just will not do. Save the money. A good one is made by Jorgensen. This one is about $65:
Then you need clamps. There are many available, but, once again, Jorgensen (their Pony division) makes an excellent line of them. Like these for about $15 each:
You may also want this four corner clamp. Again by Pony from Jorgensen, it holds the made-up frame while in glue and costs about $30:
Then you'll need a matt cutter if you plan to do anything more than frame cut outs from magazines. A mat knife will kinda do the job, but a nice bevel cutting jobbie will set ya back a fair amount. As all matt cutting must result in perfectly straight lines or it will look terrible, you woould do best to get one that rides in a jig. This one, from Logan, is a healthy $150:
I recognize that I have just blithely spent almost half a thou of your hard earned money, but if you make even a few large, very fancy frames, you'll see a payback.