MB3 191b: Replacing Feathers in a Pillow, Arranging Flowers, Gathering Salt or Fruits on Shabbos (340:8-12)

מעמר applies when you gather something from where it grows.

Replacing feathers in a pillow on Shabbos. Collecting the salt from evaporated saltwater (מעמר). Gathering fruit, vegetables, grass that's still on the ground. Gathering and arranging flowers on Shabbos.

Gathering figs and making them into a pressed cake or stringing them together.

Removing nuts that are soaking in honey.