how to make a splashboard behind sink
Are you wanting a tile backsplash? If so, first hang backboard across the area, then spread thinset on the backer to adhere your tile. Using tile spacers helps to keep everything straight. Afterwards, grout across the tile and rinse well.
There are more steps than this, but this is a basic outline for a tile backsplash
You can use contact paper or tile or even just paint it.
It will depend on what material you want to make it out of and how you want to blend with the rest of your kitchen. There's a variety of options. If you don't have an idea what you want, post a picture for suggestions and mention your preferred style.
Knowing your budget first is the most important step before any of us can help. Those pesky things, who the heck thought of such irksome things is my question. Cheers, Linda