Many of my reports feature the slicer panel that hide/show on via a button. I also include additional visuals on a page this way, such as the forecast line chart in the Supplier Insights. It is an alternative to creating another page in the report while also keeping the number of shown visuals low on a page.
For the slicer panel, I follow these steps:
In the ribbon, Insert > Shapes > Rectangle, which adds a rectangle to the page and size it and move it to where you want the panel to be on the page.
On the rectangle visual options, turn off the fill, make the line fully transparent, and turn on the background (color that the panel color you want).
In the ribbon, open the selection and bookmark panes by going to View > Bookmarks and View > Selection. The selection pane allows you to specify the z-order, or which objects are on top of others, on the page, as well as hiding and showing of objects.
Add the slicers and place them on the panel. If you are using existing slicers, you will need to order them higher than the panel in the selection pane so they are "on top" of the rectangle shape.
I typically make these dropdown slicers, with search turned on, and no background, but you can format them however you like. You can also add text boxes and other elements -- you get the idea!
Now I add two buttons, one to hide and the other to show the panel. I like to keep these in the same place off the panel (placed directly on top of each other), so the user can simply toggle the panel without moving the mouse. On the ribbon to go Insert > Buttons > Blank, then turn off icon, outline, and background. Turn on fill. I go get a menu icon from remixicons.com and click on "add image" (in the fill section). I also like to have "default state" a lower transparency than the "on hover" state, and also add a background color to the "on press" state.
Now all the pieces are created so we need to get it working. In the selection pane, hold down CTRL and click all the visuals that are part of the panel and one of the buttons, right-click and choose group. This group should be at the top of the selection list, and the other button should be directly under it.
Click on the group in the selection pane (it should be highlighted only) and add a bookmark from the bookmark pane. Click the "..." next to the bookmark and choose "Selected Visuals" so it now has the green check mark, and choose "Data" so it loses its check mark. This is super important! You can double click the bookmark to rename it, and rename it "Show panel".
In the selection panel, next to the group, click the little eye to make it hidden on the page, then, making sure that group is still the only visuals selected, make another bookmark. Same as before, "selected visuals" only and uncheck "data". Rename this one "Hide panel".
On the button outside of the group, click that one and add it's action to be the bookmark "show panel", and you can specify the tooltip as well, which I usually name "show panel".
CTRL-click the button to show the panel.
On the button inside the group, click that one and add it's action to be the bookmark "hide panel", and you can specify the tooltip as well, which I usually name "hide panel".
Now you can CTRL-click that button to test it, which should cause the panel to hide.
That's how it's created :)
Making sure your "Data" is unselected on the bookmark is very important or the slicers will reset when the panel is triggered which defeats the whole purpose.
Making sure it's only affecting the selected visuals instead of the whole page is also very important so it doesn't have any other intended impact on other visuals, and also so you can have more than one of these set up on page that work independently of each other. I did this is the supplier insights report to have "Insights" and "Forecast" visuals hide and show independently. You could even have multiple panels, such as Geo slicers, Date slicers, etc.