Shepherds Pie

I live in Arizona so there aren't many snowy nights but I still like to make tummy filling body warming meals. I decided to make shepherds pie but my version, I thought I would use sliced potatoes instead of mashed it didn't quite work out the way I wanted it to, even though I sliced the potatoes really thin with my mandolin and baked it for 40 minutes the potatoes were still raw, the flavors were there but I was very disappointed. I will try it again maybe next time i will cover in foil so the potatoes will steam then uncover so they can brown.

2 lbs of ground beef
4 tsp of olive oil
1 8 0z can of diced tomatoes
2 russet potatoes, thinly sliced
2 carrots peeled and sliced
2 cups of frozen peas
1 onion, diced
2 cloves of minced garlic
1 teaspoon of salt
1/2 of pepper
3 tbsp of flower
1 1/2 cups of hot water

Heat 2 tsp of the oil in a large skillet under medium high heat add onions cook until soften then add ground beef, carrots, garlic and salt and pepper until beef is browned. Drain off excess fat, sprinkle flour over cook for a few minutes then add water cook until fluid is thickened. Stir in peas and pour into a large cooking dish.
 In a bowl add potato slices sprinkle with salt and pepper to taste and the oil, layer evenly over meat cover with foil baked 30 minutes then raise oven to 400 degrees remove foil and bake until potatoes are brown.

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