Turn off the power leading to the spa from the GFCI breaker box. Make sure the breaker is set to off, then place a padlock on the box to prevent anyone from flipping the power back on while you're working with the spa. Empty the spa prior to removal.
Remove any plastic caps covering the screw heads you wish to remove. Pry the caps from the screw heads with the slotted screwdriver blade, then place the caps aside for later replacement.
Take a piece of masking tape and place onto each piece of the spa you'll remove by removing the screws. Label the piece in the tape with a marker and include an arrow pointing upwards. This should help you later when you have to reassemble the pieces as many of the spa parts resemble one another and can prove difficult to tell apart.
Remove the screws securing the trim to the edges and rim of the spa with a Phillips-head screwdriver. Store the screws with the plastic caps. Have a helper hold larger pieces of trim in place as you remove the screws to keep them from falling before you can lower them from position. Pull the trim free.
Remove the panels covering the sides of the spa following the same process you used with the trim. Unscrew the sides and top of the panel, then remove the screws from the bottom before pulling the panels away, exposing the spa's tub.
Clear any debris from the tops of the screws holding the spa in place against the deck surrounding the body of the tub. Use a wire brush to pull the dirt and debris free, revealing the screw head. If the screw is recessed and the wood of the deck overhangs it, then cut the opening clear with a utility knife, taking care to only remove as much of the deck material as necessary.
Remove the screws from the deck with a right-angled screwdriver, If the spa is bolted down, then use a socket wrench to remove the bolts.