Next you cut the fabric for the inner absorbent pad.
I have used a thick flannelette sheet mostly, and used 4 layers. For night time and/or heavy days, I have made some inner pads of towelling fabric which is more absorbent but slightly more bulky.
Place all the inner pad pieces on top of each other and sew round the edge
Pin inner pad of flannelette or towelling onto WRONG side of top layer
Sew inner pad onto WRONG side of top layer, round the edge and also a couple of lines of stitching in the middle if you want to. (I draw in the stitching lines with pencil otherwise I find they go a bit wiggly).