Work on stretching your hamstrings and opening up the hip today after all that sitting on the bike!
see attachment for details.

Practice your cross skills in a grassy park that offers a place to work on dismounts, remounts, barriers, hills, and a sand pit if possible.
Do 30 dismounts and remounts (mixture of barriers/hills)

Start your warm-up 40 min before your field test.
Spin easy for 10 minutes to get the legs moving. Then do:
2x10 min ON, 5 min OFF @ Sweet Spot.
Spin for 5 min easy.

20 Min Threshold Effort up a climb or on an uninterrupted stretch of flat road to determining training zones.
Find an uninterrupted stretch of road, free from stop signs/lights or longer descents. This needs to be a repeatable effort as you may test throughout the season. Your goal is to put out the hardest effort you can for 20 minutes, but also to be smooth & consistent as you perform the effort. Don't blow up in the first few minutes!

Let's work on your core strength today- here are some suggestions, see attachment
perform 3-6 sets of each

Lie on a long foam roller (if you have one) lengthwise and line it up with your spine. Bend your knees and rest your head on a small pillow on top of the roller if the back of your head does not touch without forcing it.
Rest the back of your hands on the floor and spin your palms up to the ceiling to open the chest. Lie there for 2-5 min and relax.
Then turn the foam roller sideways and roll out your buttocks, hamstrings, calves, ITB, quads ( with special attention to the inside and outside of the thigh).
Lastly roll out the lower, mid and upper back keeping your hands clasped behind your head to support your neck as needed. Arch your back to conform to the roller if you can without any pain.
If you find a really sore area, linger there for a few extra seconds- otherwise 5-10 rolls on an area should be sufficient.

Pre-Race Openers. Short quick intervals, designed to "open" your legs up for the very next days race pace efforts. Do these on your CX bike on the course (if possible). Openers: 2 x 1 min ON, FULL GAS, 2 min OFF, Then 10 min Zone 2 recovery, then 2 x 30 sec ON 1 min OFF, also FULL GAS, then 10 minutes OFF. Also perform 2-3 race starts from an imaginary start line for 10 seconds. Get in the ZONE ! ! !