Tarping is fine, although I find that more for when it's cold and windy. My doe is outside and I have straw on her hutch floor (it still drains pee into the pan underneath but keeps wind from below) and an enclosed boxed for her to retreat into if she wants, but most of the time she's sitting on top of her box enjoying the weather. The only time I tarp and blanket is when there serious biting winds with ice in the air, but I never cover the bottom.
You could always add a box with straw for those who might like the option. My minirex has a cardboard box with a hole cut out and my doe has a wooden box I made for her. IMO, it's your call on the boxes.