In Filler, players employ multi-use cards and a blend of simultaneous action selection, time and resource management, set-collection, and hand-building to collect ingredients needed to fill tasty pastries on their way to becoming the Star Baker.

Starting with a hand of three cards with various start times and basic ingredients, players choose a card to reveal along with other players to determine the turn order. The earliest player to show up for work goes first and so on around the table. Using cards from their hands (i.e., their pantry), players may use ingredients they have acquired to fill recipes from a central row of available cards (the recipe book) or restock the pantry by picking up all of their previously played cards. Each recipe filled provides new start times and ingredients to use in future rounds and may earn points that are represented by money, customer reviews, or critical acclaim at the end of the game. The availability of bonus points and cards containing special actions help to direct players' choices in the kitchen, add depth of play, and provide variety and replayability.