Planning 

When it comes to this particular domain of DIY, in order to get a good result, you have to extensively plan out beforehand how you will execute the casting/molding process. As a little kid doing molding, I had no idea how much planning was involved and how much more precision and timing is required to make sure everything lines up perfectly. 

First, we had to draw our gripper redesign floating in perspective and identify the parting line for our mold. This line would be where the two halves of the two-part mold line up later, so it was important to place along a strategic location to limit any additional damage done to the original clay model as well as put it along an axis that would be easy to fill from the top with the resin later. Since my object was mostly horizontally aligned and symmetrical, I close to place my parting line along the x-axis, in-between the overhanging flaps and the raised bump surface of the top of the gripper. 

After identifying a parting line, we had to calculate the size of the bounding box to design a good foam-core container for the mold later. Since my gripper was about 5.5"x 1.5" x 1.0", I designed a bounding box that was about 6.5"x 3.5" x 3.0". This allows the gripper a little bit of space around it to give the mold room to do its thing.