I am interested in making my own climbing holds and l just can not figure out how do they put the bubbles in climbing holds. If you take a closer look at holds, you will notice bubbled texture as well as bubbles inside. Does anyone knows process of doing this magic above?

Of course you need the texture on the outside of the holds to get grip on the holds, l assume that they just have moulds with textured surfaces and pump resin into them..
Why do you want to make your own, just for fun? It sounds like it'd be a lot more expensive to make your own than to buy them, they're not that expensive!

youre not meant to have bubbles in climbing holds it just seems like there are because its really textured on the outside. that just added to give friction. the holds are actaully meant to solid to prevent snapping.

l am sure that the bubbles are just a product of mixing the plastic resin with the fine abrasive that gives the holds their texture (it is not just cast on the surface by the mold) - the bubbles can usually be seen on the back but l do not think that they serve a purpose.

Good Luck