I made a small baby quilt for a gal at work. The top is cotton material pieced. I have some pink flannel (sorta thin but not too much)that I want to use for the backing. Do I need to use a thin batting too? Also, how to iron the flannel? And, is this combination ok to FMQ? This is my first time using flannel. Thanks to all!

I would add batting, the thickness is up to you, your quilt, your choice. You can do whatever you want and however you want.

It depends on how you intend it to be used. One thickness cotton with one thickness flannel makes a great light weight blanket for wraping the baby in. Someone gave me one like that for my first babe, 52 years ago, and I have made lots of them for gifts. Always appreciated by the recipiants.

it is your choice- but if the flannel is single sided- or thin i would add batting- it just makes the quilt softer/fluffier cozier.
flannel is nice to work with but the thin stuff can be a bit stretchy- add starch- and press carefully- do not iron around on it-and stretch it out of shape-
some of us use flannel in lots of our quilts- it makes them soft and wonderful.
for baby quilts i usually go for a good (lofty) batt instead of the heirloom thin batts...they hold up better- and with baby quilts you want them to hold up.... warm & natural is a good choice- or dream poly is wonderful

I have 2 quilts at the LA quilter now,K & Twin size.I included the flannel backing for the twin size & specified, no batting.Being used as a sofa throw, want it warm, but not bulky/heavy.
Have don't several string quilts the same way,flannel back, no batting.They're warm as toast :)

do you have enough to try a practice piece. you could try it with batting and without.

I made a small quilt (18 x 18 inches) and used batting (warm and natural) and it would not drape. Yours is probably bigger but from my experience I would not use warm and natural batting.

I recommend using a light weight batting with the flannel back. Since you are in an area that does experience cold weather, it would be nice to have the added warmth.

That's what i would do, try it and see how you like it then decide if you want batting and how thick.

Make sure that you measure, wash, dry and remeasure the flannel. Repeat until it stops shrinking. Flannel often shrinks A LOT and may take several washings till it stops. It will be thicker & softer when you are done.