I have done this many, many, many times at preschool and it never gets old... soooo fun! I usually set it up outside with the water table - after they're done playing with it we add a lot more water and soon we have colorful islands for penguins to jump off of or pirates to find treasure one.
Sensory boards made out of dollar store cutting boards and common objects from the craft cupboard and around the house. There is sand paper - kitchen scrubbies - car wash mitts - place mats - terrycloth toweling - fun fur etc. The edging is made from colourful shoelaces and each item is glued down with tacky glue - I find it stronger than hot glue - it just had to dry for a couple of days before use. The children really seem to enjoy them!