A very small and efficient addon to hide the borders of the default action bars in World of Warcraft: Dragonflight.
This will likely interact badly with other action bar addons (including ElvUI) and should only be used with default action bars.
Getting Square Icons
To get clean, square icons as shown in the screenshot above, download and install Clean Icons - Mechagnome Edition. This is a no-code icon pack that will not impact your game's performance.