first off you should make a couple small practice sandwiches---like 10" or 12" squares with top, batting, back and PRACTICE---until you get the hang of it----then when you are comfortable and happy with your hearts move onto working on your quilt!
and yes- if you are going to do (free motion) quilting you need to drop the feed dogs and use a hopping foot (sometimes called a darning foot- sometimes a free motion foot)
but you need to practice- and be happy with your quilting before starting on an actual quilt.

I would recommend that you stitch in the ditch on the sewing lines using a walking foot if you have one. If you don't have one just do all your straight lines first to stabilize the sandwich.
If you want to do a heart inside of the stitched squares, you can either FMQ or regular stitch them. FMQ with the feed dogs down (FMQ foot on) will let you move the quilt but stitch the heart shape without having to turn the quilt. If this isn't working for you, you can do a regular straight stitch (regular foot) heart by turning the quilt as you stitch the heart. Since you have already secured the quilt with the stitch in the ditch grid, you should be able to stitch the hearts.

since it is flannel, the first thing I would do, is to loosen the tension on the pressure foot...when it is too tight, it takes some of the faric with it..and it doesn't allow it to flow as it should...if it is set at 3, then move it to 1 or 1 1/2...try it

Always good to start with a practice sandwich. Even pros will frequently use a practice sandwich. I prefer to have the feeddogs in the down position and use an open toe free-motion quilting foot. Certain threads are also easier to use than some threads for free-motion quilting. I do like Sulky, but have had a wee bit more problems than using other threads. For FMQ my favorites are Aurifil or Superior Threads 40 or 50 wt cotton threads. To clarify, I do use others, but those have been the easiest for me to work with.

And, today I posted insight on a very good free-motion quilting book that is an excellent choice for those learning to do FMQ.

Some instructors say practice, practice, practice. Some say repetition (e.g. do the design ~10x and you'll have it mastered).

Enjoy!

SewCalGal
www.sewcalgal.blogspot.com

Okay I have finished the SID and then started making hearts on practice fabric. After the 6th one they are starting to look good. Think I will make a few more before trying again. Thanks for the help.