Adding Metaboxes in WordPress to your admin areas normally involves 3 steps:
This can be done much easier using Custom Metaboxes and Fields for WordPress, which is a metabox, custom fields and forms library. The library provides a bunch of custom fields and also allows you to add your own easily. Much easier to build new Metaboxes fast!
List of field types included:
Simple example from the CMB2 Github page