To start the process of opening Folders on Dock by merely one click, you first need to create Alias for the folder and add it to Dock
In case your folder pinned to Dock, unpin it (Click right the folder, Find and click on Remove from Dock in the Options sub-menu.
The second step is to open Finder and move to the folder that you want to open by a click. Click right mouse and choose Make Alias
Make sure that you add (pin) the Alias to the Dock. To perform this task, you need to drag and drop it to the Dock. Hold for seconds and then release it. Now the Alias is pinned to the Dock.
After you click on the Alias, the folder in Finder will be opened. Single-click it.