First, combine flours in a bowl with your pinch of salt, and make a well. Set aside and work on the lard.
Draw a half cup of water from your pot of boiling water and mix it into your lard, stirring gently to melt it. If the lard is in a metal bowl, place it on top of the boiling pot of water so it heats it up gently. Stir every once in a while, scraping down around the sides of the bowl.
Let the lard water cool a bit, and then pour into the flour well and mix. Turn the mess out onto the table, and knead gently till it's one dough ball.
Flatten into a disk, wrap in cellophane, and put it in the fridge to rest for at least a few hours.