New landscaping beds

I've always used landscape mix to build the beds. Mulch on top. Used Plant Tech's and Clegg's, both worked well for me.

I usually don’t bother with soil. Although it doesn’t hurt obviously

I have a big pile of rotting shredded bark that I use to fill or make beds with, and then just keep adding too as it rots down. If you plant shrubs eventually they’ll root to your subsurface clays and be fine. Shallow rooted stuff like flowers and ground covers can live happily just in the loam

that will be fine for flowers.
i usually start a new bed at 6-8", then just keep adding to the top every 6 mos or so till i get a foot-ish. most important thing is to never turn the bed...just keep adding to the top and let the fungi make its magic happen

make lasagna not mashed potatoes

What do y'all use to stop erosion?? I feel like a lot of the dirt would run off once it gets more than a few inches above ground

The below is the edging style I like to use, I like the crisp look but also a little natural. Plus makes it easy to adjust the bed shape if you choose without moving a more permanent border.

But it does well holding in everything. I've just never really made any NEW beds before.

I’m getting older (74)and don’t want to stoop much so I bought four 6x3x2 ft high corrugated metal planters. It’s going to take a ton of stuff to fill them. I’m thinking bedding mulch topped by raised mix I have from Clegg’s, bought last year. Going to save my back in the long run, if I don’t ruin it hauling stuff this year.

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Was curious how high to go, is 8-12" raised above the level of the grass pretty standard for landscaping?

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This is exactly what I do in building new landscape beds, using the garden soil/garden mix/landscape mix referenced by others - it’s just composted forest products with some sand mixed in.

It settles down over time with compaction and with decompostion of the garden soil, so a 12 inch high bed, may be 6 inches high after a couple years. Slightly elevated landscape beds, even as little as several inches, make all the difference in the world to the health and growth of woody landscape shrubs in poorly drained heavy clay soil common to south LA and elsewhere. The vast majority of landscape shrubs do not like “wet feet” associated with planting at lawn grade.

I personally shoot for 12 inches as I like the as aesthetic look of a higher raised bed, but I would suggest a minimum of 4 to 6 inches. And I also build them as you are contemplating - either use non-selective herbicide to kill the grass where the bed will go, or cardboard/newspaper on top, and then the garden soil planting mix on top. And of course mulch on top after planting - I favor pine straw, but that’s me, but mulch, whatever you choose to use, is very important.

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I have a question on the same line as OP. I need to build some more beds. We use the 4” metal border. With the settling and compaction of the bed builder do you just add more soil in a couple years? Necessary to remove mulch first or add on top and let it compost?

Also, is it necessary to leave drain holes in the metal edging? I find our current bed holds water after a rain.

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Yes - for the first several years I would add additional garden soil to the beds as it settled and decomposed. However, as the shrubs grew in/filled out, I stopped doing it. The shrubs, by and large, stay near the same height as the original planting as the roots anchor them in.

I add garden soil on top the of the mulch - I do not remove it first.

I don't use edging, but if you feel/observe that a good amount water is being retained in the beds, to sogginess, for 2 to 3 days following rain, then it would probably be a good idea to add weep/drainage holes in the edging. Root rot, from excess moisture, will kill many shrubs with higher frequently than drought (as during drought people will water their shrubs) - bottom line, a well-drained landscape bed is important to the health of most landscape plantings.