Put the Mylar bag on a stable, flat surface, with a heat resistant surface above it.
Put the flour into the Mylar bag. Be sure to pack tightly.
Test the distance of the top of the Mylar bag to the heat-resistant surface. Make sure you’re able to lay the top of the bag on top of the surface so that it can safely be heated with the iron.
Put a piece of tin foil on top of the packed flour.
Open up one oxygen absorber and place it on top of the tin foil.
Quickly but carefully place the top of the Mylar bag on the heat-resistant surface and put the hot iron over it to seal the bag.
Leave a 2-inch opening in one corner.
Insert the narrow vacuum attachment into the 2-inch opening and turn on the vacuum. This will remove most of the oxygen from the Mylar bag and your flour.
Remove the vacuum attachment and seal the remaining part of the Mylar bag with the hot iron.
Write the date and contents on the side of the Mylar bag with permanent marker.
Place in airtight 5-gallon buckets, seal and mark contents and date.