Make (2) 1/2" x 3/4" x 8" wood cleats that match your shelf. Push a torpedo level into the corner and mark level on each wall. Draw a level line from the mark into the corner on each side. Run a bead of paintable caulk along the cleat, interrupted in two spots for hot melt glue. The hot melt will hold the cleats to the line until the caulk sets up. Caulk the shelf to the top of the leveled cleats and when the caulk sets up, this will easily hold ten pounds.

The size of the shelf means nothing to us without knowing the size of the fireplace. I think the fireplace currently has a modern, streamlined vibe. A shelf here to me would look like extra clutter, but it's really your personal preference.

We did ours like this, with a similar corner (though it looks like you have a little more space between the sink and the stove wall, so might want to wrap the corner). These shelves are 18.5" off the counter, which was intended to allow for uppers to go there in the future (though we are now 12 years post-reno and haven't done that yet, so may never get to it!) One thing I would do differently is the tile behind the range--it was supposed to meet the hood but for reasons I can't remember anymore, the spacing was off so the tile extends slightly beyond the hood and we had to end it short to avoid it looking really odd. The hanging utensils bar was a fix when it still looked strange. There were also supposed to be two shelves on the right side, but we realized all the bottles we wanted to keep there would hit the top shelf, so decided to put the second in another area of the kitchen instead. In general, we planned these based on what we wanted to store on them (and mapped out the whole kitchen for that at the time we renovated). If you plan to do a gut remodel at some point in the future, it probably doesn't matter as much how far up you tile or where exactly you place the shelves as long as it works for you now. Our shelves and tile were also all DIY, so if you have a contractor they can probably get more creative on solutions and placement. (We were not up for opening our plaster walls, for instance, even though that would have been the way to get the ideal placement of the shelves since you could then place blocks.) Also yes to a good range hood (and know that even with that, you will get some grease on items on the shelves--though it's been much better than I expected, and we really only have issues with it on the oil shelf where items are right up against the range). The primary issue on the long shelves is just dust, but we definitely expected that and give it a good clean a couple times a year, which seems to address it enough for our needs. YMMV based on your tolerance for that!

Aloha @Floored You: TileDesigners Thank you for the questions. I was hoping it could be fastened with an adhesive vs the wood. Was hoping for feedback if that would be a good option. We had water damage to our kitchen so since we had to tear out the drywall, we thought we should try to make the kitchen how we’d like it to be. Electrical is where it was previously located. There were high cabinets before. This is a cookie cutter style house for this subdivision we are in. Cabinet height is 34 1/2”.