The simple way to design cushion is using EPS in plates and add the plates on all 6 sides of the product as illustrated. But you are only seldom able to do so. If the product is 600 x 300 x 400 mm and have a weight of 5 kg the static load is 50N/(0,6 m x 0,3 m) = 0,28 kN/m2. That is way out of the area. In this case the cushion is too hard and a shock will work through the cushion and damage the product. In the other end of the cushion curve over 15 kN/m2 of the cushion would have been too soft. In the last case a shock will work all the way through, damage both all the cushion and at last also hit the product.
You have to redesign the cushion or choose other materials. The design can be as the following.