The 18-year-old has signed a new 18-month contract with Bolton.
Sampson has also agreed to join Southend on a one-month loan deal. The deal could be extended to last until the end of the season.
Sampson said: “I’m delighted that I have signed this new deal and I’m looking forward to my spending my long term future at Bolton.
“I feel like I’ve matured a lot as a footballer in the last few years and I hope that I can continue progressing as I have done over the recent seasons.”
