Using a serving plate, scoop guacamole in the middle of the plate. Take a large enough piece of plastic wrap and mold the guacamole into a circle (see photo above).
Using a small plastic bag, add the sour cream to the bag. Using the warmth of your hands, gently press the sour cream in the bag to make it slightly warm and easier to pipe. At the corner of the plastic bag, cut a small tip off and practice a little pipping on a plate (see photo above). If you are not getting the desired amount out of the bag, make the opening a little larger.
Starting from the inside of the guacamole, make 3-4 circles of sour cream.
Using a butter knife (starting from the middle circle of the guacamole to the outer circle of the guacamole) gently run the butter knife from the middle circle to the outer circle to create the “web effect”. Then do the same on the opposite side of the guacamole circle and continue to work your way around until complete.
Decorate with plastic spiders or any of your favorite Halloween decorations.