Rinse the cranberries under cold water and pick out any that look shriveled or soft. Drain them well and add them directly to the slow cooker insert.

Add the sugar, orange juice, orange zest, cinnamon, ground ginger if using, and salt to the slow cooker. Stir everything together so the sugar begins to dissolve and the berries are coated. No need to add water. The orange juice and the moisture from the berries are enough liquid.

Place the lid on the slow cooker and cook on LOW for 2 1/2 hours. You do not need to stir constantly, but give it a quick stir once at the 1-hour mark and again at about 2 hours. By 2 1/2 hours, most of the berries will have burst and the sauce will look jammy and thick.

Check the consistency at 2 1/2 hours. If the sauce looks thinner than you want, remove the lid, switch the slow cooker to HIGH, and cook uncovered for 20 to 30 more minutes. The extra time lets moisture evaporate and the sauce will firm up noticeably as it cools, so do not over-reduce it.

Turn off the slow cooker and stir in the vanilla extract. Taste the sauce and adjust sugar or orange juice if needed. If you want a very smooth sauce, press it through a fine mesh strainer. For the classic chunky style, leave it as is.

Let the sauce cool in the slow cooker insert for 20 to 30 minutes, then transfer it to a jar or airtight container. Refrigerate until ready to serve. It will thicken further as it chills, reaching a nice spreadable consistency by the time it is fully cold.