If the Bible is 100 percent God's word and all true, does that mean slavery is ok during certain situations?

Since God didn't ban slavery in the Bible, he set rules kinda regulating it. Such as if you buy a slave you have to let them go free after 4 years, and if they disobey you can beat them as long as you don't kill them. If that's in the Holy Bible, than slavery can't be that bad, right?