If you use baseball card pages the slot card may fall out easily when flipping pages or carrying the binder. Business card pages are more secure but don't allow the cards to be in any sort of protective sleeve. Just make sure whatever pages you use are archival quality.
For boxes, baseball card boxes work pretty well as do business card boxes. If you want baseball card boxes try BCW (https://www.bcwsupplies.com/), they offer a multitude of sizes. I find their 880 count baseball card boxes fix my storage shelves pretty well and hold over 300 slot cards in protective sleeves pretty well.
I actually use a mixture of both... binders with storage pages for rarer cards so I can see them better and baseball card boxes with protective sleeves for all the common cards just to handle the bulk. I now have over 100,000 cards in my main collection with another 200,000+ doubles so everything is working for me.
I covered storage options and ideas along with other information during my presentation at the CCA convention in Las Vegas this year. The club has not yet posted the video of my presentation but I did post the slides and my presentation notes on my website where the Slot Card Guide is available (www.slotcardguide.com). There's also the slot card portal at www.slotcardexchange.com where you'll find links to both of these websites along with other resources for slot card collecting.
If I can help in any way just ask.