Enable the 2D Dock

If the 3D Dock isn’t your taste, you can use Terminal to switch to the 2D visual implementation.

defaults write com.apple.dock no-glass -boolean YES

Restart Dock with the following command:

killall Dock

Revert to the default setting:

defaults write com.apple.dock no-glass -boolean NO

Restart Dock

3D

2D

Screencast: