I've made several of the kits from Lazerlinez many of them flag kits.
When inserting the stars make sure you let them sit in soapy water for a minute or two, makes them go in a lot easier. After putting in a few stars roll the blank on a hard surface to make sure they are seated. When all the stars are in I wrap the blank with masking tape then use thin CA on the inside of the tube. Turn using a sharp skew. Once I turn enough to remove the tape and bring the stars down to the level of the blue I flood the wood again with thin CA. This makes sure the stars are glued in and fills any gap between the stars and the blue. I do this with the strips too. Finish with a sharp skew taking light cuts. When trimming the blank to size do not use a barrel trimmer, use a sander.
Hope this helps.