What happens next?

How to make your cat's basket a castle
Keep your cat away from its basket.
Give it a place to roam about for an hour or two, so that it will not get bored and interfere with your decorating.
Cat proof the area that your cat will be in, to make sure it does not ruin anything.
Empty out any loose dirt that your cat may have brought it from outside. Go outside with a dustpan and brush, and brush the bottom of the basket with it to get any mud off.