Set out phyllo dough to thaw at room temperature for roughly 2 hours (still in package).
Open one roll of phyllo and begin to separate sheets. If it is too moist and is sticking together, let it sit for a while to dry out. If it is too dry and brittle, wring out a damp wash cloth and place it over the sheets for a few minutes. (this step can technically be skipped, but it helps the assembly step (step 8) move much more quickly in the long run)
Cook bacon in a medium pan on medium heat. Set the cooked bacon aside to cool.
Chop the first bunch of spinach into quarter-sized pieces. Melt 1 tbsp butter on a large skillet. Cook the spinach, stirring constantly until it all looks wilted. Set aside to cool. Then repeat with the second bunch of spinach.
While the spinach is cooking/cooling, crush the bacon to bits into a large mixing bowl.
Once spinach is cooked and cooled, drain it by squeezing thoroughly over a sink. The drier it is, the better. When dry, put spinach into mixing bowl with bacon. In a small saucepan, begin to melt the remaining butter on low heat.
Mix the feta, mozzarella and Parmesan cheeses into the mixing bowl. Add the minced garlic, garlic powder, onion powder, nutmeg, oregano and salt to the mixture. Stir thoroughly using your hands.
Preheat the oven to 375°F. On a cookie sheet, (it may be lined with aluminum to minimize the floury mess) lay down one layer of phyllo. With a pastry brush, gently brush melted butter onto the phyllo. Be careful not to saturate the phyllo with butter and watch out for rips and tears. Once the first layer is lightly buttered, place another layer of phyllo on top. Butter this layer as well (still lightly). Fold both sheets of phyllo in half lattitudinally (hotdog style). Grab a small handful of the cheese/spinach/bacon mixture and squeeze it to compress. Place the clump at one end of the phyllo and proceed to fold the phyllo in right triangles like you would a flag. from here, you may either freeze and save it for a later date or you may proceed to the next step.
Place all completed spanakopita on a different cookie sheet. Lightly glaze every piece on top with melted butter. Place in the oven for roughly ten minutes or until golden brown. The cook time varies with how much stuffing is inside the phyllo.
For storage, it is better frozen if it has never been cooked. If it has been cooked, store it in the fridge for up to a week.