There’s a slipper pattern in Quick Tricks to Crochet #293:

And it looks very simple, but it has a lot of parts you have to sew together. So, here’s a quick photo reference of how it all goes together using the names of the pieces from the pattern:

(Note: The trim on the finished slipper is not in the pattern; I just did that for a better fit.)

From left to right: Top Heel Piece, Bottom Heel Piece, Bottom Sole, Cardboard Insole, Top Sole, Upper – Instep, Back Piece, Finished Slipper

Top Heel Piece and Bottom Heel Piece sewn together.

Top and Bottom Heel Piece Sewn to Bottom Sole with Cardboard Insole in place.

Top Sole sewn to Bottom Sole and Top and Bottom Heel Pieces.

Upper – Instep sewn to the Soles.

Back Piece sewn to Upper – Instep and Soles.

As mentioned above, the trim was something I did on my own to make the slipper fit a bit better. If you need it as well, go down a full millimeter in hook size and work four rows of single crochet, working decreases at the upper corners. Try on as you go to get the fit you want.