Follow instructions on resin packaging for mixing. You'll want to mix 4 oz. of resin. Use a separate measuring cup for each part. Once equal amounts of both parts are measured, pour them into a mixing cup. Gently stir the two parts together for 3 minutes. When you start to stir, cloudy swirls will appear.
Attach the Legos to the frame, brushing a little bit of resin on the bottom of each Lego and securing to the frame. Let set for 20 minutes. Leave the rest of the resin in the cup, as you have about 30 minutes working time.
Toward the end of the 20 minutes, make a wall around the frame with painter's tape. Press it all the way around the frame, as closely and tightly as possible so none of the resin leaks.
Pour a layer of resin onto the frame. Use the torch to remove any bubbles. Allow 24 hours for the resin to harden.
Remove the tape. Round the edges with sandpaper. Remove any dust. Tape off the back of the frame to keep the resin from running over onto the back.
Mix the remainder of the resin, about 4 oz., according to the instructions you used the first time. Pour resin over the entire frame again and let the resin go over the edges to cover the sides. Let set for several hours.
Remove tape from the back of frame. Let the resin completely set overnight.
Video
Notes
While mixing, make sure to scrape the sides and bottom of the mixing cup to fully incorporate the two parts. Continue to mix until the cloudy swirls no longer appear and the mixture is clear.