I don’t know if this is applicable to your case, but I would recommend looking up the local building codes. Expansion joints usually have to be done when a certain amount of feet of concrete has been poured, so you might need one even for such a small slab.

Also, make sure you’re not pouring directly against the foundation. If it’s poured too close, it can cause a lot of problems. You should create a gap between the slab and the foundation, then fill it with some type of filler material.