You are right - the step explaining this got lost, somehow.
You need to set the action property of the text box in the table containing the "slicers" to Go to Report
Report name - [&ReportName]
Add three parameters:
Country => [CountryName]
ReportingYear => [@ReportingYear]
ReportingMonth => [@ReportingMonth]
This will cause the report to refresh
The rdl file in the updated resource file shows this.