That’s just the default “finish” ready-mix concrete will have after you’ve stripped the forms off (generally smooth but with some little gouges where there were air bubbles). For starters, check out this tutorial from Apartment Therapy for small planters. You can probably imagine how to scale up from there using larger containers as your form. For larger, rectangular planters like the one in the photo, get a book from your local library about concrete work. You’ll find the information you’d need in there to build larger forms, likely out of plywood.