Normally, the answer is 'yes'. But in this case, flax seeds won't work the same. Chia seeds have an outer coating that absorb water and create a gel-like consistency. This makes them ideal for thickening foods like jam and pudding. If you don't have chia seeds, you could mix a little cornstarch or arrowroot powder with cold water, and slowly add it to the simmering strawberries until it reaches the consistency you like. I haven't tested this method, so I can't recommend amounts, but if you try it, let me know in the comments how it works, and how much you use!