Using pure beeswax, a totally natural and food-safe material, you can make it as good as new.
This requires very few tools and can be done by a DIYer of any skill level. You can get beeswax at any crafts store. It will take about an hour to set up, complete the repairs, and clean up.
Your cutting board should be clean and dry, let It sit for a few days without use or washing. If you can, put it in the oven for a few hours at low heat. The warm and dry wood will allow the melted wax to flow better and be absorbed readily into the fibers.
Step 1: Prepare Cutting Board
The wood may have expanded from moisture near the cracks. Use a plane or knife to flatten any raised areas.
Step 2: Prepare the Beeswax Filler
Step 3: Fill the Cracks With Molten Beeswax
The best technique is to pour the molten wax just outside the crack, and let it flow in. It may be drawn into the crack by capillary action if conditions are right. When the wax you've poured becomes opaque, but still is soft, use the bottom of the spoon to work it into the crack. Remove excess wax with the spoon and deposit it in the melted wax container for reuse.
Work down the length of any cracks in this way, then use the pick to probe for bubbles or gaps in the wax filling. Fill any voids using the same method.
Step 4: Clean Up the Joints
If you time it right, the wax will have hardened in the crack and only partially on top (say the texture of Vaseline)
It will take a while to get a passable surface, and may require additional applications of wax, as brittle wax may chip out of the crack fillings as you clean then up.
Step 5: Seal the Cutting Board
If you like, you can use the remainder of the beeswax to seal the cutting board, making it easier to clean and longer lasting.
To do so, dilute one part of the melted beeswax with three parts food-grade mineral oil while applying heat. Simply rub the hot solution onto all surfaces of the cutting board using a rag. ( I find that this is a perfect use for mismatched socks, since they fit over your hand )
Allow the wood to absorb the mineral oil, drawing the dissolved beeswax into the pores.Use more rags or paper towels to wipe off the excess after a few minutes.
That's it! You're all done. Let it sit overnight for best results, but it's usable pretty much instantly.