This tutorial by snowbillr covers creating your own buttons in Phaser 3:
"Phaser 2 had buttons but they aren’t built in to Phaser 3. In reality, they are simple to make on our own. In this tutorial we’ll break down what it means for something to be a button and how to make one in Phaser-land.
Buttons Aren’t Scary
Buttons aren’t some magic black box of mystery. A button in its simplest form is something that responds to clicks.
That’s it.
Hover states, animations, fancy effects, whatever, are just icing on the cake. Phaser makes it really easy to make something clickable, so let’s start with building that."