I like to have some way to do this while out of the house.
These are ways that I've tested and have found to be practical. But your mileage may vary.
One of the easiest options. Ideally the keyboard supports switching between multiple connections.
I have the iClever BK05S, and really like it. Each key is full-size, but it's still pretty compact when folded.
Downsides: It costs ~$45.
I do two things to make this more convenient:
Upsides: It's very compact to carry with you, and it works with most keyboards, including Logitech's Unity receiver and other dongles.
It's much more convenient if you can rotate Android's screen upside-down. This way, the OTG cable is positioned at the now-top edge of the phone, and you can place the phone on a stand.
Android apps that allow you to rotate the screen 180°: [1]