The first temporary counter base ended up being too long. It was going to hinder the installation of our new cabinets (they arrive in early Feb), so I took it out and made a new, simpler counter base.
It fits our big microwave (which N reminded me didn't fit on the first one) and took much less time to fabricate. The old one is now the base of a table in the workshop downstairs. This one will become a laundry folding table once the new counters go in.