Just FYI, cardboard is full of fire-retardant chemicals. I would caution against using it in the garden as those chemicals will leach into the soil. That can offset balance by harming bees and, if you're consuming crops, then you will also be consuming those chemicals. As far as slugs, snails and other insects, a combination of Organic DE and crushed egg shells works brilliantly. The egg shells cut the soft pests and the DE cuts the ones with an exoskeleton.
Just FYI, cardboard is full of fire-retardant chemicals. I would caution against using it in the garden as those chemicals will leach into the soil. That can offset balance by harming bees and, if you're consuming crops, then you will also be consuming those chemicals. As far as slugs, snails and other insects, a combination of Organic DE and crushed egg shells works brilliantly. The egg shells cut the soft pests and the DE cuts the ones with an exoskeleton.