My snap-in petal soaker is then a top "layer" of 1 layer cotton velour and 1 layer of heavy bamboo fleece. The bottom layer/petal is 2 layers of regular weight bamboo fleece. The pieces are serged together and then just stitched together across the very top with the snap going only through the bottom petal.
View of the soaker snapped into the shell.
Higher rise setting.
Lower rise with the umbilical snap snapped-down.
For a larger size fitted, or a night-time fitted, you'd need more petals in your soaker, or you could use a long-fold soaker. The goal is just to keep each sewn layer thin for easy washing and drying.
If I were to make this same diaper with T-shirts or just jersey or flannel, I'd use 4 layers for the shell with the elastic running through the middle. Then 3-4 layers for each petal in the soaker. :)