Lay on your back, hold your legs up with your thighs straight up and your calves parallel to the ground (knees bent!) Then put your baby on your calves and sort of hold her on with your hands as you extend your legs and bring your legs back in.
Another good ab exercise is called a "renegade row" Get into a plank/push-up position with your feet wider than your hips. Now, do a row on one side. If you can do it with a hand weight, awesome. If you can, do a full set on one side then switch, if you can't do it with a weight, switch arms on alternate reps. Baby can lay on your mat and get kisses.
Another fun one is a plank where you walk your feet around. Either do a simple "out out in in" pattern between shoulder width and as wide as is comfortable, or do a semi circle with little side steps. Another good baby kissing exercise.
Do remember that it will also take time for your skin to bounce back, and also if you're generally back in shape except for a poofy belly you should check for diasis recti:
Lay down as to do a crunch, feel for a separation as your shoulders come slightly off the mat. Most instructions for it will tell you to just lift your head, but there's a small separation that happens for most people at that point that will, unlike true diasis, go away as the shoulders come up.