The surgeon first makes an incision into the skin, then the subcutaneous tissues (source). They then go through the fascia, which overlies the rectus abdominis muscles. This consists of two layers.
After this, the surgeon enters the abdominal cavity. In most cases, the surgeon can then encounter the uterus. However, in some cases, the surgeon is met with the omentum, bowel, bladder, and other aspects.
Once the surgeon encounters the uterus, they can make a bladder flap. But with women who have had c-sections before, this is difficult.
There are three more layers to go: the perimetrium, myometrium, and endometrium. Once through these three layers, the surgeon can break through the two layers of the amniotic sac and deliver the baby. This whole procedure only takes a few minutes.