1.

Add some CMC to the sugarpaste. Keep on adding the CMC gradually until you feel that the paste gets thick (you have to use quite a lot of pressure to knead it). The paste needs to be thick/firm so that the squares won't lose the shape.

All squares need to be the same thickness (if they are not the same thickness it will be visible and you won't get a neat finish). To get the same thickness of all squares I used spacers to roll out the paste.

To make 3 mm spacers I stuck two lollipop sticks (each 1.5 mm thick) together with double sided tape. Since the sticks are short you might have to reposition the spacers to roll out the whole piece of paste.

To avoid cutting out too many squares I suggest rolling out a few pieces of paste, sticking the squares on and making more later once you run out of them.

Leave the pieces of paste to dry for a few minutes (or longer, depending on the amount of CMC added). The paste can't be too stretchy (soft) because the squares will lose the shape.

2.

Squares are square, right? Yeah, I thought so too ;) until I had the chance to use different brands of cutters ;) Most of the cutters available on the market have slightly rounded corners. To make a checkerboard I suggest using the ones with square corners ;) I used Fine Cut cutters.

Before cutting the squares out, make sure that the paste doesn't cling to the board. If it does - flip it to the other side and allow the underside to dry for a few minutes.

After that time flip the paste back to the other side. Place the cutter on the surface of the paste. Press the cutter firmly all the way down to the board. Once the edges of the cutter reach the board make a few circular moves on the board (as if you'd like to rub the edges against the board). Lift the cutter. If the paste stayed in the cutter rub the edges with the surface of your hand (clean cut). Gently push the paste from the cutter. When holding the cutter don't press it from the sides - if you do, you will damage the shape of the cutter (it will no longer be a perfect square and you'll have difficulties with making an even checkerboard pattern).

3.

Leave the squares to dry for some time. Meanwhile cut out the rest of the squares. If the squares are quite firm, press them gently from the top with a smoother to even them (sometimes the corners are raised slightly after pushing the squares out from the cutter).