My Baby Takes forever to eat!!

Rebekah
Hi All,
My baby is 3 weeks old and eats 3-4oz every 3 hours. The doctor said this is great and totally normal! 
However it is taking her 20-30m to finish each bottle. Sometimes she will even start to fall asleep, but if I put away the bottle thinking she's done. she will fuss! And so it really does take that long for her to get her fill. 
She is a formula baby, breast feeding isn't an option for us unfortunately. I tried a slightly larger nipple hole, but then it just dropped all down her front, I think she needs to stay on the low flow newborn one.
The up side is she never spits up! 
Is 30m a normal amount of time for a baby to finish a bottle? What do people do during feelings to coordinate holding baby and bottle for that time?