I'm 2.5 weeks postpartum and still incorporating some basic inner core exercises to move my abs back together as well as a whole lot of pelvic floor strengthening exercises (which are awesome for pregnant women as well!) Here is a circuit I did a couple days ago. 3-5x through, 10-12 reps each movement.
1. Glute bridges
2. Leg lifts into heel slides, both sides
3. Bridge marches, both sides
4. Bird dog
5. Dead bug
6. Knee thrust into knee fall out, both sides
It's been super hard to be patient, (and I sure miss my friends in the weight room), but I'm still just walking every day and doing these simple exercises to allow my body to heal fully. It will be worth it!