Hi Andrew;
Welcome to Permies! I hope you get lots of
permaculture info and ideas on here. It's the best place I've found for meeting like-minded people, and getting advice, info, and ideas.
So! On to your questions. And bear in mind I am not a hugelkultur expert - these are just some things I've experienced, and have heard/read from trusted sources.
1. Clay is awesome! It holds water well, and
generally also has lots of nutrients. I've been adding it to my buried wood beds. I would use the clay on the
inside of the hugelkultur. Get it nice and wet, and put it on - maybe mixed with some organic matter - as one of the lower layers. The plant
roots will grow down deep and get the water and nutrients. You could put some on the top layer of soil, but I would definitely mix it with other soil or organic matter. And mulch it well so it doesn't dry out and crack.
2. Both of those woods should be perfectly fine.
3. It all depends on when you're planting, but for the first year it's great to get some cover crops in there to
boost nutrients. A good cover crop of legumes will help to add nitrogen, which will be lacking in the beginning as it is tied up in the
carbon. If you're short on organic matter, a cover crop mix is a great way to grow your own. It also depends on what you plan on eventually growing in the hugelkultur. Is it for annual veggies, berries, perennials? It would be good to get something growing on it as it goes into winter, as the roots will help to hold it together so you don't lose surface soil.
4. Deer. Yeah, I have an 8 foot
fence around my garden. The only way you can keep deer out of a garden is to
fence it. You can plant things that deer don't eat - but that's a pretty short list around here.
Plus, they will probably come and taste it anyway, to see if they like it, and then walk all over it, just 'cause they can.
The only way it will be more successful in the shady part is if you grow shade-loving plants on it. If you're growing veggies, flowers, or berries - probably won't be great.
5. Fall is a great time to build a hugelkultur. The premise of these earthworks is that they soak up copious amounts of rain water/snow melt during the wet season, thus needing less irrigation in the
dryer months. So, having it built going into winter is perfect. It will soak up water, and the innards will start to break down and get ready for spring.
Hugelkultur beds are said to really hit their stride in their third year. So the first couple of years you will probably have to water to some extent, depending on the size of your hugelkultur, and what you are growing in it. Really big ones are better at absorbing and holding lots of water than small ones, obviously. So, the smaller it is, the less water it can absorb, thus the more supplemental water you will probably have to add.
And that is my two cents worth. Let me know if you found this helpful, or if you have any other questions!
Cheers
Tracy