Put your ruler inside a plastic cup and mark the cup twice using a thin permanent marker. Your first mark will be at 3/8 of an inch, and your second will be at 3/4 of an inch.
Set your timer to 2 minutes and have a craft stick ready for stirring. Slowly pour resin into the cup up to the 3 /8 inch line. Keep in mind that an accurate pour is crucial, so don’t be too generous with your pour. Next, slowly pour the hardener to the 3/4 inch line, making sure to not go over it.