Lakes like that can sometimes be tricky.. I would think bottom content/structure will play more of a role than depth.. What I mean is find a weed line or transition from hard to soft bottom.. It's really hard to tell without knowing the lake just by the map but the bottom left side of the lake is where I would start looking in the 10-20 foot range.. I'm going to assume the water is of average clarity so I would plan on lowlight conditions.. One of the main problems some people have in targeting walleyes is assuming they will bite during the day..on average clarity to clear water, especially in the winter, you will never catch them even if it's overcast until the sun hits the trees.. Lots of variables to that but it's a good rule of thumb.. Especially if your just learning a lake, don't waste time and frustrate yourself, stick to the evening bite.
If that area doesn't pan out I would set up right on the break of 35-15 in about 25 feet.. Also if there is a shelf on top of the break that stays 15 feet deep or even goes to 5 feet you will find fish there
