I work mostly with dried flowers, mosses, or other natural items. Because these objects are so light, I often have trouble getting them to stay in place while the resin cures. Should I just wait longer for the resin to start curing before I pore it into the molds? I don’t want to miss my opportunity to work out bubbles by waiting too long.
I would suggest pouring in more layers. For example, you might want to pour your first third, let it start to cure, then pour your next third. Place the flowers in the middle third and allow it to start curing. Finish with your last third. You are right in that waiting for the resin to cure, then placing your flowers, makes it more likely you will introduce bubbles that will be hard to get out later.