Remove sealed phyllo dough from the package and thaw overnight in the fridge or for at least 3 hours at room temperature.
Cut the sweetened guava paste into 16 slices of the same size and thickness.
Preheat the oven to 390F (200C)
Prepare your workstation: bring phyllo dough to room temperature and unroll sheets onto a smooth and dry surface, and cover it with a slightly damp clean kitchen towel (this prevents the dough from drying out). Uncover to remove phyllo sheets as you work with them, then promptly the remaining sheets covered with the kitchen towel.
Open one sheet of Phyllo on a flat working surface. Working from the edges toward the center, lightly brush one sheet of phyllo with melted vegan butter or oil. A silicone brush works well for this. If not available, you can use the back of a large spoon to spread the butter or oil. Be careful because the phyllo sheets are fragile and break easily. Top it with a phyllo sheet and lightly brush the edges. Fold the dough starting from the larger side; you will end up with a long piece of phyllo dough. Place one slice of guava paste in the left upper corner of the dough and fold it down diagonally to cover it. Keep folding it diagonally up and down until the end of the dough. The size of the phyllo sheets may depend on the brand. I used Athens phyllo dough for this recipe, and the sheets are 8 1/2 x 13 inches (21 x 33 cm).
Brush the edge to seal and turn the seam down. Slightly brush the top with melted butter or oil. Repeat the process until all pastries are assembled.
Place the pastries 1 inch (2cm) apart in lightly greased large cookie baking sheets and bake for 8 minutes or until the phyllo starts to brown. Remove from oven.