When you look outside and see a gray sky, it might be tempting to feel discouraged at the uninteresting backdrop and plain light quality, but flat light can actually be some of the best light to work with as a photographer. If you would like to see why flat light is actually such a boon for portrait photographers, check out this helpful video tutorial that features an experienced photographer guiding students through building a shot.
Coming to you from Jiggie Alejandrino, this great video tutorial shows the versatility of flat light for portrait photography. Rather than thinking of diffuse, even light as boring, this sort of flat light should be thought of as a neutral palette. Instead of having to fight the natural lighting to get the look you want, you are free to build it up however you want. If you use flash, you can easily create a dramatic look or just augment the natural light a bit. Or, if you are shooting natural light only, you can design your composition and backdrop as you see fit without much worry about light direction, then use dodging and burning in post to shape and emphasize your subject as you see fit (particularly with the post-processing latitude of modern sensors). Check out the video above for the full rundown from Alejandrino.