Time to actually read the Constitution. You are technically right, it was "bound persons", not "slaves".
Article 1, section 2, paragraph 3
(Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons.) (The previous sentence in parentheses was modified by the 14th Amendment, section 2.) The actual
Enumeration shall be made within three Years after the first Meeting of the Congress of the United States, and within every subsequent Term of
ten Years, in such Manner as they shall by Law direct. The Number of Representatives shall not exceed one for every thirty Thousand, but each State shall have at Least one Representative; and until such
enumeration shall be made, the State of New Hampshire shall be entitled to
chuse three, Massachusetts eight, Rhode Island and Providence Plantations one, Connecticut five, New York six, New Jersey four, Pennsylvania eight, Delaware one, Maryland six, Virginia ten, North Carolina five, South Carolina five and Georgia three.