1, Make a Rectangle or square Box "whatever" > No color for Fill > 2 pt, Stroke.
2, Make a Line with Line Segment Tool >
With the line Selected > Window > Stroke > Check Dashed line > set Weight of line to 1/4.
(or whatever size to get even B&W Squares)
You may need to adjust Dashed and gap Line, Spacing also to get the size Checks you want.
3, Select Click and hold Line > press Alt on widows>
Drag line, (This makes a copy of the check line.)
Line up second line >
Re-size and Repeat as needed to get the size and amount you need >
Place in Box or adjust box to Checks.