To classify tasks into quadrants each task needs to have a pair of labels. A label that tells how much effort it takes to complete the task and another one that tells how valuable the task is.
To do this, in Label settings we'll create two Label groups: "Effort" and "Value" where the former one will contain "high-effort" and "low-effort" labels and the latter one will contain "high-value" and "low-value".
Because a task should have only one of the labels from the group, both groups will be turned into an " Exclusive group" by editing settings of the label group.
Checking on the second option will make it easier to add label to a task by hovering it and then choosing one of two labels from each group.
Creating Smart Lists
Since each Matrix quadrant is associated with a Smart List there should be 4 Smart Lists which will filter tasks based on the combinations of "Effort" and "Value" labels. These Smart Lists should look like following:
These Smart Lists filter out items on Backburner and based on their combinations of labels they filter out tasks.
If you're unsure how to do this, please read an article on Smart Lists.
Making the Matrix
Now that you've created these 4 Smart Lists you should turn on Matrix strategy by going to Strategies menu.
In Matrix settings you can enter a title for quadrant and then connect it to the Smart List by using "Choose Smart List" drop-down menu.
Workflow Snippet download
If you wish to use this exact setup or have trouble setting this up, please download Effort/Value Matrix snippet.
Once downloaded, you can load it in the Workflow Library by going to Import/Export tab.