In the bowl of a stand mixer, combine the buckwheat flour, tapioca starch, brown rice flour, sugar, salt, and yeast. If you are using molasses, just put it on top.
Put the psyllium in a second medium size bowl. I recommend using a 1 ½ quart Pyrex (or glass) bowl, which you can use again for the rise.
Heat 10 ½ oz of water to 130 degrees F. Pour exactly ¾ cup (6 oz) of warm water into the bowl with the psyllium and stir to make a gel. Add the vinegar to the gel.
Add the psyllium gel to the flour mixture along with the oil. Give the mixture a stir. Add remaining 4 ½ oz water, stirring with a heavy duty scraper until mixed.
Put the mixer on the stand and use the paddle to mix for 2 minutes. The mixture should look like muffin batter, but will be stiffer and have some elasticity to it. Scrape the sides of the bowl and beat with the paddle for another two minutes. Scrape sides of bowl. Add the wild rice and walnuts and beat until mixed. Scoop out about ¼ cup of the dough and set aside. Add the cranberries and beat with the paddle just until they are blended in.
Turn the dough onto a pastry mat very lightly slicked with oil. Form dough into a round, then use the reserved ¼ cup of dough to patch up/cover any exposed cranberries (this prevents them from drying up in the heat of the oven).
Scrunch up a piece of parchment paper and press it into a 1 ½ liter or so glass bowl. Cover with a piece of greased plastic wrap and let rise for about 35 minutes. It will not double, but it will puff up substantially.
While the dough is rising, place a Dutch oven and its lid on in the oven and preheat the oven to 450 degrees F. Note: If your oven is really slow to preheat, you will need to do this earlier in the process since the dough only needs 35 to 40 minute sto rise.
Carefully remove the hot Dutch oven from hot oven and set on a cooling rack or safe spot. Lift the parchment paper with the dough and set it in the hot Dutch oven. Cover with the lid and return pot to the oven. Close door and set timer for 25 minutes. After 25 minutes, remove lid from the pot and bake for another 20 minutes or until bread is browned and crusty.
Turn off oven. Remove the loaf from the Dutch oven and set the loaf (no parchment) directly on the oven rack. If you are worried about sesame seeds falling off, you can put a baking sheet on the lower rack. Leave it in the closed oven for about an hour. This helps dry up any excess moisture that could contribute to gumminess.
Let cool completely before slicing. This is very important. The loaf should feel very hard. Let it cool, you can even chill it if you want to make it easier to slice, then use a really good bread knife to slice through that thick, chewy crust.