How can you make a sun funnel for safe solar viewing?

Well honey, you can't just stick your head up and stare at the sun like you're trying to win a staring contest. Grab a cardboard box, tin foil, and some scissors. Cut a hole in the box and tape some tin foil over it, then poke a tiny hole in the foil to let sunlight through. Voilà, you've got yourself a fancy DIY sun funnel for safe solar viewing. Just don't come crying to me if you blind yourself looking like a derp out there.