Not enough can be said about powerful legs in swimming. If you never work your kick you'll never have fast underwaters or an even stroke. Here is leg burner!!
Below are links to the Equipment I used (or new versions) on Amazon or reviews on this site:
Kick Board: https://amzn.to/3aH17yL
Goggles: https://amzn.to/2QaeopS
Warm Up:
2 x 500 @ :20 rest 300 free, 200 IM(kick, drill)
8 x 75 @ 1:10 back 25 rt, 25 lft, 25 swim
Main Set: 3 x (6 x 150 @ 1:40, 1:50, 2:00 or 1:45, 1:55, 2:05 #1&2 – free breathe every 3rd 80% #3&4 – 100 free, 50 nonfree 90% #5&6 – 50 free, 100 nonfree(can be IM) FAST 50 @ 1:00 easy choice)
Kick:
3 x (100 @ 1:40 kick strong
2 x :20 fast vert. kick @ :40
2 x 75 @ 1:20 build
4 x 25 @ :25 kick FAST)
18 x 50 @ :50 w/zoomers
Odd – 25 build swim choice, flip, 25 fly kick on back fast
Even – 25 free smooth, flip, 25 fly fast w/1 breath max
Breast:
8 x 75 @ 1:15 brst
25 pull w/free kick
25 2k1p
25 swim
300 choice wd