There are several ways to do it but if you are having problems keeping food stocked on your counters the best thing would be to leave the bakery open and run your heart rating right down. This will slow the number of diners coming in and thus slow the food consumption down. When you serve the food on the counters it will take them longer to consume it all giving you some time to build up your food stock.
To "close" the diner just turn your chairs away from the tables so the bots can't sit. Or allow them access to the host table but to no chairs and tables.
See this thread as well,
https://forum.storm8.com/showthread.p...ght=Block+door