Which lane should remain open first?

Keep the narrow right cyan reservoir lane open until its stream has settled; it supplies the later cyan bar.

Why delay the bottom-left red placement?

That cell is the landing space needed by the final cyan receiver after the magenta gates disappear.

Sand Blocks level guide

expert 5 colors

Level 286 threads a cyan reservoir down column 6, opens two magenta 2x3 footprints, and reserves the bottom-left red cell for the final cyan landing.

If the player asks you to sign in, open the video on YouTube instead.

From the upper cyan source, place cyan 1x3 horizontally at r1c1-r1c3; place yellow 1x3 at c2,r2-r4 and green 1x3 at c1,r2-r4. Leave source lane c6 and r1-r4c6 empty.
Route red 1x2 to r5c1-r5c2, then cyan 1x2 to r5c3-r5c4; wait for the right counter to pass 20% before touching r5c6.
Move the upper magenta 2x3 into its six-cell footprint r2-r4,c4-c5, keeping c6 clear; after it reads above 70%, move the lower magenta 2x3 to r6-r8,c4-c5 and wait for 100%.
Drop yellow vertical into c3,r5-r8, then green vertical into c2,r5-r8; verify each receiver reaches 100% before opening the lower-right outlet.
Place red 1x2 at r9c1-r9c2, route the final red bar to r9c4-r9c5, and leave r9c3 open for cyan clearance.
Send cyan 1x2 from c6 to r10c3-r10c4, then place the last green vertical in c5,r8-r10; wait for both 100% states and the empty-source transition.

Colors in this level:

Cyan, Yellow, Green, Red, Magenta

Dropping the long magenta receiver directly under the right outlet before the cyan stream is clear.
Filling the bottom-left red slot before the green bar has opened the lower lane.
Moving both magenta gates at once and losing the settling path for the red layer.

Board notes 5 details

Layout: Portrait board with a narrow right cyan reservoir, two red outlets, dense left yellow/green/red/cyan receivers, and two large magenta rectangles in the center-right column.
Goal: Clear the small left receivers first, drain the cyan lane, then open both magenta gates before the bottom-right green and red finish.
Opening: Stage cyan, yellow, and green receivers in the upper-left lanes while leaving the right reservoir unobstructed; wait for the cyan stream to settle.
Danger Zone: A long magenta receiver under the right outlet seals the cyan lane; an early bottom-left red placement removes the landing cell for the final cyan bar.
Mechanics: Two side outlets, phased cyan/red feeds, large magenta gate rectangles, and a late green/red bottom-right finish are evidenced.

Which lane should remain open first?
Keep the narrow right cyan reservoir lane open until its stream has settled; it supplies the later cyan bar.
Why delay the bottom-left red placement?
That cell is the landing space needed by the final cyan receiver after the magenta gates disappear.