With Bookatrix cards you NEED a box as they are about 1" thick when they stand away from the base card.
I particularly like to emboss a line around the edge as I feel it gives a focus to the centre and provides a corner to place a small embellishment and add a bit more detail.
I like to decorate the box lid with a motif or wording which complements the event the card is for.
I had a bit of a disaster with the rubber stamp though. I embossed it using gold embossing powder straight onto the box lid and the heat from the gun made the box warp !
I made another lid and cut the first one up so I could use the image and layered onto gold paper. It does stand out better on the lid now though. The peeloff is from a sheet I bought from Partners. The rubber stamp is a Denami designs one that I bought from a forum friend. I think it is so elegant.