Combine 1/2 cup of spelt flour with 1/2 cup of filtered water in a glass bowl. Stir well, scraping down the sides of the bowl. Cover with a clean tea towel and let it sit at room temperature for 24 hours.
On the second day, pour out and discard half of the flour and water mixture. Add 1/2 cup of flour and 1/2 cup of water, mix well, cover, and set at room temperature for 24 hours.
For days 3 through 5, repeat the instructions from day 2. Discard, feed, stir, cover, and keep at room temperature 24 hours.
Continue the steps from days 2-5, but begin feeding every 12 hours now, rather than every 24 hours.
After one week, you should be seeing signs of activity. With the feeding schedule and fermentation time, enough wild yeast and good bacteria should be present to attempt your first rise. Look for bubbly foam on top, airy bubbling throughout the starter, or doubling in size.
Start baking with your sourdough starter. Store in the fridge if not using daily. Feed once a week in the fridge or every 12-24 hours at room temperature. The ratio will be equal portions of the starter, water, and spelt flour, with perhaps some adjustment for the spelt flour as it can produce a thinner starter.
Notes
A warm environment will bring a quicker rise to your starter, whereas a cooler environment will slow it down.
Spelt flour absorbs water a bit differently than whole wheat flour, so you might find your starter is thinner when using the typical 1:1:1 ratio of starter, flour, and water. It takes a little longer for it to absorb the water. So one minute it will seem very thin and the next it will thicken up.
Aim for a pancake batter consistency, which may mean you don't use as much water during feedings.
You can measure the growth of your starter by placing a rubber band around the jar at the beginning level of you starter. When the starter has risen past the marker, measure the growth and timing of your starter’s peak activity. This is often somewhere between 4 and 12 hours after feeding. Spelt starter may rise and fall quicker than other flours.