two methods of removing bubbles.

Put your just mixed thermoset plastic into a vacuum chamber. This pulls all the bubbles out.

Hit the thermoset plastic with a blow torch. This causes the bubbles to expand and pop on the surface. You can only do so much thickness with this.

When pouring you may want to pour in layers. Use vibration to get bubbles loose from the stuff you put into the thermoset plastic.

And, of course, pour slowly, into the bottom of your form. Never on top of your stuff. Pouring on top of the stuff, makes air bubbles trapped underneath the ledges.