Soak your paper in a plastic bin with water and 10 % alum mixed in. I used about 2 cups of water and 3 tablespoons of alum for about 15 minutes.
Soak your leaves in water and 1% ferrous sulfate or homemade iron water for 15 minutes.
Set the first alum soaked paper on the glass trivet or ceramic tile.
Arrange leaves on the paper.
Cover with a second piece of treated watercolor paper.
Next, add a sheet or two of brown paper as a buffer.
Repeat with a new card and leaf arrangement.
Continue with more paper and leaf arrangements.
Finish with another glass trivet or ceramic tile and tie the bundle tightly together with twine or string.
Set in an old non-food use roaster pan or pot covered with water.
Bring to a boil and then reduce the heat and simmer for 1.5 hours.
Remove from the water and let cool.
Cut the string and open the bundle to reveal your prints.
Set on towels or hang the paper to dry.
Upon drying the paper may curl. Flatten by covering the curled paper with brown paper and lightly ironing or set some heavy books on top.