When using a date slicer it would be great if it existed an option "earliest date" (or latest). The issue is that when you have a table that is constantly adding new records, with a date column, ...
The workaround can also be used for periods, in this case, you would need to calculate which is the period of interest, e.g. Last Month, this is explained in the last part of the post.
What I have also done in these cases is to add buttons where the user can either choose to see the last period available (a month in the picture below) or choose the wanted period.
When the latest period is selected, a bookmark that hides the slicer and activates a page filter for "latest period" is activated.
When the "Show all periods" is selected, the slicer is unhidden and the page filter is deactivated.