For the first tier, you will need about 35 newborn or stage 1 diapers.
Unfold 17 of them and, one at a time, roll them up tight, starting from the front of the diaper and rolling it to the back. The tighter the better. Place a rubber band around the center after you roll each diaper up to hold it tight. These are the inner diapers for the cake.
Take the cake platter and place the 8-oz baby bottle or large bottle of baby lotion in the center. Then place about 5-6 diapers around the bottle and put a large rubberband around the entire ring of diapers.
Next, form a 2nd ring with the remaining 11-12 diapers by placing them around the 1st ring of diapers. Complete it by placing a large rubberband around the 2nd ring.
Now for the final ring of diapers for the 1st tier: Take 18-20 diapers, unfold each one, roll them up tight like before, but instead of a rubber band around each one, tie a thin, 1/4 inch piece of ribbon around the middle around each one. Then place them around the second ring to form a 3rd ring. Now take a large, 1/2 to 1 inch wide ribbon and tie it around the entire tier to hold them all together in a circle shape.
(Note, you could use just rubberbands around each diaper for the 3rd ring if you have opaque ribbon to hold the 3rd ring together. The important part is that no rubberbands are showing when you are done.)
The second tier is made much the same way, only instead of 3 rings, you will only make 2 rings of diapers. Just like the 1st tier, the inside ring will need about 5-6 diapers. Part of the 8-oz bottle will be sticking out of the 1st tier, so place your 5-6 diapers around it to form the 1st ring of the 2nd tier. The 2nd ring will need 11-12 diapers. Place a ribbon around each one of those 2nd ring diapers and hold them all together in a circle with the 1/2 to 1 inch wide ribbon, just like before.
It is probably easiest to assemble this tier on a table and then place it on the rest of the cake after it is assembled. So, take a 4-oz bottle and place it on the table.
Then take 5-6 diapers and roll them up like before and tie them with the thin ribbon.
Then place them around the 4 -oz baby bottle and tie your wide ribbon around it to hold it together tightly in it’s shape. Take the top tier and place it on the top of the cake.
Add little baby items like Pacifiers, bottles, lotion, bibs, receiving blankets, miniature stuffed animals, baby towel, onesie, wash cloths, baby hygiene products, toys, etc. Place them between the folds of the diaper, tuck the larger items into the outer layer of ribbon.
Add stickers and decorations to match the baby shower theme.
Place a stuffed animal, pair of baby shoes, or something else on top to match the baby shower theme.
Voila, a diaper cake.