Shelley Fine you’re welcome! They are a bit pricy when compared to regular wall plates, but they look much cleaner and modern.

Are you installing a new junction box, or will you be replacing an existing one? Are you installing the junction box where you have access to the studs (new work box) or will you installing it where you already have sheetrock hung (old work box)? You would need a 3 gang new or old work junction box to accommodate 3 switches. If you have metal clad cable (aka BX cable) you'll need a metal box, if you have NM-B (nonmetallic-sheathed cable aka Romex) you can use a plastic or fiberglass box. Junction boxes for receptacles/outlets and switches are pretty standardized height and width wise so it won't be too small or too big. However, you can purchase different depth boxes if you need additional room for wires, but that won't affect height and width. For example here's a plastic new work box (amzn.to/2A4JN5X) and old work box (amzn.to/2A4pd5I) that I have used with the Lutron Claro 3 gang screwless wallplate (amzn.to/2pOKCtu). I hope this helps - feel free to click on the links and purchase them from Amazon.