Here is a good video Heidi, https://www.youtube.com/watch?v=V2CYF7StJOk
here's one WOW... https://www.youtube.com/watch?v=9e6WeQeBjOI here are ideas/videos https://www.youtube.com/results?search_query=diy+dog+house+for+big+dogs
Did you try googling "dog house diy plans" it will give you links and images so you can see what materials you're going to need.
My various dogs over 25 years at the same house with a fenced in yard, never once went into a doghouse we had built for them. Not once. I would have been better off buying some outdoor dog beds every few years up on a deck. Just my humble experience. The only thing I ever saw in the dog house was bees.