I have been doing a lot of thinking since my post on Monday about what it means to make a sacred space. Yesterday morning, I again went to the Kotel (Western Wall) for shacharit (morning prayers) as well as to try and gain a deeper understanding of the sacred spaces question. I came away with two models of sacred space.
Model 1: Inside-out
The Inside-out model is essentially the Ohel Mo-ed (Tent of Meeting) or Beit Hamikdash (Holy Temple) methodology. In this model the holiest area can be found at the center, and then the kedusha gradually decreases as one moves from the center. The holiest location was off limits to even the High Priest, save for one day a year, Yom Kippur. Moving away from that critical center, the holiness decreases, although never entirely dissipates. I would recommend finding a good diagram of either the Ohel Mo-ed or the Beit Hamikdash for better visualization. Some chumashim have them in the reference section. To review, a place is anointed as holy, and then the sacredness flows from that area.
Model 2: Outside-in
Exactly the opposite of Inside-out, and the model with which I believe is most relevant today. This is the model of the independent minyan, sometimes the synagogue, and perhaps even a beit midrash (house of study). Here, the people bring the holiness into a space, and ascribe the holiness to the location. For example, Kehillat Hadar which meets on the Upper West Side of Manhattan, uses the basement of a local church to hold their Shabbat morning activities. Chairs are set, an aron kodesh (holy closet) is stationed and eventually equipped with a Torah. The participants arrive, engage in davening with great fervor, and read from the Torah. However, once the davening has concluded, the space is transformed back into the basement of a generous church. The behavior, set-up, mindset, and intention of the kahal (community) brings the kedusha. Thus, we bring holiness to a place by behaving appropriately, dressing appropriately, having a focused intent, and gathering the dispersed holiness into a critical mass.
Please be advised: these are not criticisms of Kehillat Hadar, nor are they a knock on the holiness of the church as a whole.
I wish you luck on transforming your spaces, Shabbat shalom.