Apple introduced third-party keyboards back in iOS 8, and swipe-input options like Gboard, SwiftKey, and Swype made typing on and iPhone one-handed much easier. Even better, apps like Word Flow moved the keyboard to the side of the iPhone so there was less thumb-stretching. Now, in iOS 11, Apple added an option for better one-handed typing right into the stock keyboard.
To use the new one-handed mode in Apple's default keyboard, just make sure you're running iOS 11 on your iPhone. With that out of the way, the rest is just too simple.
When using the stock Apple keyboard, just tap long-press on the globe icon to bring up the keyboard menu. Below the list of keyboards, you'll see icons for left, center, and right orientation. If you use your iPhone with your left hand, choose the left orientation. If you use your iPhone with your right, choose the right orientation.
Whenever you want to return to the center position, just tap on the arrow opposite of the left or right positioned keyboard to expand it back to full width.
While I love this new one-handed feature, it's not enough to make me want to switch from my preferred Gboard keyboard. If Apple implemented swipe input, I might finally switch back full time.