There is a difference between:

• Being given "some food", which at the master's discretion may be enough to keep you alive, or not.
• Being given a piece of papyrus entitling the bearer to draw X pounds of barley from the food bank, where X is set out in a contract and you can sue if you don't get it, and moreover the slip is a negotiable currency - you can use it to pay for clothes or rent or whatever.

As interesting as it may be, I think you are getting into more of a philosophical argument than a historical discussion. How one defines a slave can range from chattel slavery where a slave can be bought or killed at their owner's discretion, to debt bondage where a person is bonded to work for a certain duration to pay off a debt but otherwise has some rights. Some quite serious people would even define governments, salaried jobs, or marriage and childbirth as slavery, though I would disagree with them on all accounts. It can be like prostitution or pornography - sometimes it is hard to define but usually you know it when you see it.

American slaves were not paid in food or housing. There was no contract or agreement between the slave and the master regarding the arrangement. The slave made no choice to become a slave in the first place, much less the method of his payment or the duration of his term . Food or housing could be withheld capriciously by the master despite performing a days labor.

Some Romans voluntarily enter a state of slavery to satisfy debts or crimes. Rousseau would argue that selling oneself into slavery is still slavery since the person now enslaved loses his rights and moral agency despite doing so willingly.

I am not an expert on Egypt, but my understanding is that the labor was done as an exchange similar to a feudal obligation, and that food and housing was provided for laborers. While feudalism is certainly a dark-grey area on the slavery spectrum, it would be a hard case to lock down.

The big point is, that the Egyptians were put to work either voluntarily, or that they were put to work because they didn't pay taxes. Also, each adult citizen there had to do a certain amount of work per year (it usually wasn't a whole lot). I'm not a historian, but I do know a couple things about ancient Egypt.