Sowing on raised bed

Last year the sweet onions were devoured from below in a few days, so I'm trying something else this year.

We got a cheapo willow raised bed in gamma (1x1m) and 200l of potting soil. I put it at the back on the driest and sunniest spot in the garden, added two small scoops of dried cow and chicken manure, mixed, watered and sowed:
At the back all along the back, a mix of dill and cucumbers for pickling (Lidl), in ribbons. I didn't separate the three bits (dill-cucumber-dill) not sure it was meant to or not.
A bit further two rows of sweet onions, one of red and one white (Aveve), in ribbons.
Next a row of chard, on the left a packet from Brico (Central Park), on the right some I bought in Spain (Batlle).
On the very edge I spread some basilicum (Central Park).
All of these, larvae, slugs and snails I'm sure would be happy to devour again. Hoping the location, bed and new soil will be a deterrent, we'll see.
It's probably too sunny a spot for the chard and basil, though. Possibly the dill as well. The bag inside the bed has handles, but doesn't look like it would be easy to move once full.