Newbie Router Question

Hey all, Not new to woodworking in general but fairly new to routing and finding the array of bits overwhelming! I want to make some post-it note holders for gifts for family members for Christmas. Want to route a 3x3 square recess into blocks of wood to hold a pack of post-its. Have an acrylic template to route the shape of the square recess. What bit or bits would I need to accomplish this? Im on a budget and don't want to spend $100s on bits right now. Google tells me I need a flush trim bit with bearings on top and bottom. But when I search that it gives me so many types and sizes! Figure it would be best to ask here and hope those with knowledge on this subject will share with me! The bit Google is recommending would be the bit to follow the template and route out the outside shape of the square but would I need another one to finish removing all of the remaining wood from the middle of the square recess? Just looking for the best tool/tools for the job so I can batch these out quickly and efficiently! One that will give me a nice flat bottom to the recess and crisp sides so I'm not sanding forever on each one. Thank you in advance for your time and expertise!