I admit I tend not to use Slicers often - I find filters do the job in most cases - but for this particular spreadsheet I need to make it as easy as possible for others to view and use.
I've got a few pivot tables in my workbook across various worksheets, and there tends to be 3 or 4 pivots for each. With the single selection ones it's really easy - point, click and the data shows as it should. The issue I've got is that I know the users will want to select more than one option. For instance, I've got one slicer with a dozen or so options, and I expect that the majority of people will select about 3 or 4 options (any combination). The slicer would need them to deselect 8 or 9 of the options though which doesn't seem the best way - especially when there are other slicers they'll want to use as well.
The best that I can think to do is keep the slicers to select one option, and then let additional options be selected through the filter. Ideally for a multi select slicer, (I think) I'd want the first option selected to be a SELECT, and anything not selected would be DESELECTED, so that anything else clicked would be added rather than needing to click through and remove all unwanted ones. Is that possible? Is there a better (perhaps more obvious) way of keeping things as simple as possible for the users?