Apparently one stomatopod wasn’t too impressed with his new home in the lab. So he took matters into his own “clubs”. He punched away at the plastic at one end of the cavity to make a second entrance. The photo shows the damage he made to the lid (the lid is screwed onto one end of a tube, the other end has an opening for the stomatopod to enter and exit).
If the field, I think they punch away at the rubble that they live in too. By doing this they can make the cavity into the shape they like and they can expand it if it isn’t big enough for them. However, it’s unlikely that they create the hole from scratch, other animals (e.g. boring sponges) probably start the cavity. Stomatopods just renovate.