If you have an old slate floor, and you don't like the look of it anymore, but you don't want the work and expense of ripping it out, one easy solution is to lay a floating floor over it. Floating floors are not attached to the subfloor in any way, but merely sit on top of it. This means that you don't have to alter the underlying floor in any way, so if you change your mind in the future, you can pull up the floating floor and still have your original slate floor.
Pry the trim off the walls around the edge of the slate floor, using your pry bar and hammer. Keep the trim intact as you remove it. Set it aside.
Lay plastic underlayment over the surface of the slate in slightly overlapping courses. Cover the whole floor.
Link your first two floorboards to each other, snapping them together at the ends. Put them on the moisture barrier, next to the wall where you want to start, at one end. Set spacers between the boards and the wall to create a thin gap.
Set additional boards off the ends of the first two, snapping them together and setting them down with spacers between the boards and the wall. Cover the whole starting edge of the floor.
Cut the last board in the course to fit at the end, using your miter saw.
Set the second course of boards in place by linking each new board along the long edge of the first course. Arrange the boards so the ends don't line up between the two courses. Use your miter saw to cut the last boards of each course as needed.
Repeat, building across the floor course by course, covering all the slate.
Cut the final course of boards lengthwise on a table saw to fit along the ending wall. Leave a half-inch space between the cut edges of the boards and the wall.
Reinstall the floor trim, using a hammer and trim nails. The trim should hide the spaces around the perimeter.