use '?' for JOKER (blank)

From letters B, A, C, K, S, T, R, E, T, C, H, E, S  I made following words

13 letter words

backstretches[26]

11 letter words

backstretch[24], backstreets[19]

10 letter words

backstreet[18]

9 letter words

sketchers[18], backrests[17], scratches[16], catheters[14], stretches[14], earthsets[12], tesseract[11]

8 letter words

checkers[19], rechecks[19], resketch[17], sketcher[17], sketches[17], backrest[16], brackets[16], backsets[16], setbacks[16], breaches[15], seecatch[15], batchers[15], brachets[15], catchers[15], cratches[15], hektares[15], cathects[15], restacks[14], stackers[14], searches[13], breathes[13], cheaters[13], hectares[13], recheats[13], teachers[13], escheats[13], brashest[13], starches[13], sherbets[13], catheter[13], chatters[13], ratchets[13], chastest[13], acerbest[12], accretes[12], scarcest[12], starkest[12], earthset[11], theaters[11], theatres[11], shatters[11], cateress[10], cerastes[10], abetters[10], berettas[10], casettes[10], cassette[10], scatters[10], estreats[8], restates[8], retastes[8]

7 letter words

checker[18], recheck[18], chebecs[16], hackees[16], hackers[16], ketches[16], backers[15], rebecks[15], bracket[15], backset[15], setback[15], beckets[15], beaches[14], braches[14], creches[14], screech[14], kashers[14], shakers[14], batcher[14], brachet[14], catcher[14], hektare[14], batches[14], cachets[14], catches[14], scratch[14], cathect[14], beakers[13], berakes[13], sackers[13], screaks[13], betakes[13], rackets[13], restack[13], retacks[13], stacker[13], tackers[13], baskets[13], caskets[13], tackets[13], reaches[12], bashers[12], brashes[12], chasers[12], crashes[12], eschars[12], breathe[12], cheater[12], hectare[12], recheat[12], reteach[12], teacher[12], escheat[12], teaches[12], bathers[12], berthas[12], breaths[12], chaster[12], rachets[12], ratches[12], sherbet[12], etchers[12], retches[12], sachets[12], scathes[12], behests[12], thecate[12], chatter[12], ratchet[12], stretch[12], accrete[11], retakes[11], skaters[11], strakes[11], streaks[11], streeks[11], tsatske[11], hearses[10], aethers[10], heaters[10], reheats[10], rashest[10], trashes[10], theater[10], theatre[10], thereat[10], hatters[10], shatter[10], threats[10], tethers[10], straths[10], creases[9], beaters[9], berates[9], rebates[9], cerates[9], creates[9], ecartes[9], ectases[9], basters[9], breasts[9], actress[9], casters[9], recasts[9], cresset[9], resects[9], secrets[9], abetter[9], beretta[9], casette[9], batters[9], scatter[9], betters[9], tercets[9], bassett[9], stactes[9], easters[7], reseats[7], searest[7], seaters[7], teasers[7], tessera[7], estreat[7], restate[7], retaste[7], estates[7], starets[7], staters[7], tasters[7], retests[7], setters[7], streets[7], tersest[7], testers[7]

6 letter words

chebec[15], hackee[15], breach[13], breech[13]