The Montessori way to teach numbers and make them concrete to toddlers with spindles they can hold in their hand. This makes it easy to associate a number with a quantity.
It also introduces 'zero' in a very comprehensible way.
To introduce this material to your child first remove all the spindles from the box, then work from left to right, clearly say the number and then count aloud while you place the correct number of spindles in each compartiment.
Control of error: there are exactly enough spindles to complete the exercise correctly. If there are not enough or some left over, it will be clear to the child that there is a mistake.