The Confederate Constitution was the constitution that the Confederate States of America created for themselves.
It is mostly a word-for-word copy of the US Constitution at that time, but there are some telling differences. Unlike the original's indirect mentions, it explicitly mentions slaves and slavery, officially protecting it:
Article I, Section 9:
No bill of attainder, ex post facto law, or law denying or impairing the right of property in negro slaves shall be passed.(Confederate Constitution's addition bolded). Also, Art IV Sect 2 states that one could freely transport slaves through the Confederacy, and it also strengthens the language stating that escaped slaves shall be returned to the states that they had escaped from. Art IV Sect 3 states that slavery shall be legal in all territories ruled by the Confederacy.
However, the author of Constitution of the Confederate States of America- what was changed? concludes
In the end, however, many of the most interesting changes introduced in the CSA constitution have nothing to do with federalism or slavery at all. The President's term limit and line-item veto, along with the various fiscal restraints, and the ability of cabinet members to answer questions on the floor of Congress are all innovative, neutral ideals whose merits may still be worth pondering today.The President of the Confederacy was limited to one six-year term.
- Constitution of the United States The modern version