I just potted a sedum in the top and left the sides empty until another day. Same problem! I was going to plant alyssum in the sides. Portulaca would look good too. They do settle down eventually. I've potted several of them in my life, but never with strawberries.
Oregano?

Hi
I grow strawberries in mine lol I use palm citrus media along with some long fibered sphag at the openings . have to start at the bottom and pack rather tightly as you go up.
Only use it during winter gary

This worked pretty well for us: Put a plastic garbage bag in the pot first. As you fill it with dirt, just cut slits where the bag shows through the hole. Then place the plants through the slits and continue filling with dirt. Then cut off the extra. (Make sure you poke a hole in the bag for the very bottom drain hole too.)

This year we did one side with strawberry plants and the other side with impatiens. The flowers really look good... A big mass of color. Much better than we expected.

Using a plastic bag like that probably also makes a huge difference in retaining water. I have a strawberry jar sitting on the back porch that I haven't used in years because it's hard to keep anything watered in there in the heat - water evaporates through the clay. I may try it again with a plastic bag liner.

I think it does help with the water retention. Had that issue too. Using a "dripper" to water the strawberry pots this year (a one gallon plastic milk jug with a small hole poked in it). That seems to be working well at getting it more evenly watered.

hi
I use a piece of PVC pipe drilled with small holes in the center . This allows watering from the inside out . On the 10 gallon i use 2 inch pipe with 1/8 holes with endcap at the bottom. gary