One of the safest ways to heat the contents of a glass bottle is simply to put the filled bottle under hot running water until the milk reaches the desired temperature. (howtoadult.com)
If you have problems cutting the slices, warm the blade of the knife under hot running water before cutting each slice. (joyofbaking.com)
There is no need for electrical outlets or hot running water which makes this warmer perfect for travel or anytime you are not at home. (pregnancymagazine.com)