Start with the feeling.
Lay out the menu, scoreboard, bossbar or hologram. Upload the exact PNG you want and place it with precision down to 0.1.
Give the world rules.
Create items, creatures, effects and commands. PlaceholderAPI connects live player and world data without turning the editor into code.
Make it playable.
Publish the pack, test with friends and update without restarting the server. The visual layer disappears when a player leaves the place.