You can pour a small concrete slab yourself as long as you plan and prepare. Concrete is difficult and costly to remove once it sets if not done properly, so be sure to take the proper precautions:
Make sure you have enough concrete before starting.
Measure and install your form carefully.
Wait until the weather is dry and warm before pouring.
Remove grass and vegetation before starting.
Coat the wooden for with oil or a concrete release agent for easy removal.