Choose Words of the Week or Month. 
Core words can be chosen based on a pre-determined curriculum from school or through a wall chart or core words of the year.
Read books that include words of the week. Highlight or sticky note ‘target words’.
 

Use a Word Wall.
Have learners add pictures, objects, remnants, text, etc.  that define, categorize, or semantically relate to the target words.  Use photos of learners engaged in meaningful language experiences and the target core words.  For example, if the class made a big dirt pile and the target word was “more” as each learner added “more” to the pile, take pictures of each child adding the dirt. Then put those pictures under the word “more” on the word wall, or put a few small plastic bags of dirt on the word wall.  Just remember to put pictures or remnants of multiple ways “more” was used (e.g., with the dirt, with snack items, with “more” balls, etc.
 

Create Word of the Week/Month Books or Boxes.  
These can be tangible books, boxes, folders with pockets, talking power point books, talking photo albums, etc. Books and boxes are great for working on core words in a commenting communication function.  For example, if “like” is the core target word, learners can help collect things they “like” for one book and things they do not “like” for another book.
 

Create additional communication boards/visual boards made up only of fringe words
When learning about a particular theme or subject, create a board based on the words you know will be used for that theme or activity. Some of these may be added to the talker, but initially it is easier on a separate board so you are not spending time searching for fringe words.
E.g. Learning about space - sun, moon, planets, satellite, space suit, astronaut, etc.
The boards can be used and pointed to in conjunction with core words using speech, sign or AAC.
 

How to build language using core words