This book http://volthauslab.com/wp-content/uploads/2016/05/225303report55.pdf (Analog Integrated Circuit Design) has some sample opamp designs with transistor sizing provided in Chapter 6 (page 266 and some others) for a 180nm CMOS process. They should work decently with only minor adjustment for the skywater 130nm process, so it seems like a good place to start for analog design blocks.