Here are what happened on the 3rd try:
1. didn’t grind the almond meal (didn’t seem to make much difference last time I did it) but did sift before weighting
2. beat the egg white longer than before. didn’t look very stiff or stiff enough. (maybe i should test out just the beating next time)
3. for the 2nd tray of cookies, i squeezed the batter out with the tip closer to the mat.
4. baked at 135C at first but seems not cooked still after 15mins so turned back to 140C. still took some time for the bottom to be cooked.
5. for the first batch, i put another tray above it hoping to block out some heat so the top won’t overcook. but the heat flow somehow made the cookies go out of shape. so for second batch I only put in the extra tray on top after 10mins or so.
6. the 1st batch turned out to look okay but cookies from the 2nd batch were mostly hollow.