With wood slabs you will find often holes and cracks which go all the way through the piece. Sometimes we leave the cracks alone and just stabilize the loose parts within the crack. But often we seal the cracks with resin. To do so we cover up the underside of the slab with newspaper + resin to create a seal. Once that is dry we flip the slab around and pour resin from top. The picture shows the underside with newspaper + resin combo.