Get a box you think will be big enough for your kitty.,
Cut some small holes (about 1 inch or 25 mm in diameter is good) for air exchange in the box.
Make sure the bottom is secure, and reinforce it if necessary.
Take a plastic bag that will fit at the bottom of the box.,
Shred up some paper and put it in one side of the box.
Put some old towels in the other side of the box.
Finally, put the kitten in and put something on top as a cover.
,,, Use it to line the bottom so urine will not soak through, should your kitten have an accident.