Preheat oven to 350 degrees F.
In a medium pot, bring stock (or water) to a boil. Add the freekeh, cover and reduce heat to low. Simmer until all liquid is absorbed, about 20 minutes. Remove from heat and let sit, covered, for 5 minutes.
Cut the acorn squash in half and remove the seeds. Brush with half of the olive oil and roast, face down for 25-30 minutes, until soft.
While freekeh is cooking and squash is roasting, heat the remaining tablespoon of olive oil in a large skillet over medium heat. Add the onion, garlic, celery, and apple and saute for 3-4 minutes. Add the salt, pepper, thyme, walnuts, and sunflower seeds and saute for another couple of minutes. Then add the baby spinach and saute until just wilted.
Add the cooked freekeh and the sauteed veggies to a large bowl and combine. Adjust seasoning to taste.
Divide mixture into the halved, pre-cooked acorn squash. Serve as is, or, if serving later or melting cheese on top, bake for 10-25 minutes just before serving.
